Ultrahigh efficiency spray drying apparatus and process

ABSTRACT

The disclosure relates to ultrahigh efficiency spray drying systems and processes, utilizing induction of localized turbulence in a drying fluid flow stream to produce spray dried product, having particular utility for low temperature spray drying operations. In a specific implementation, a method of processing a spray dryable liquid composition to form a spray dried product includes the steps of: generating a spray of the spray dryable liquid composition; contacting the spray of spray dryable liquid composition in a spray drying contact zone with a stream of primary drying fluid; injecting pressurized secondary drying fluid into the stream of primary drying fluid in the spray drying contact zone at multiple loci thereof to provide localized turbulence at said multiple loci; and recovering the spray dried product from the spray drying contact zone. Systems of the present disclosure are effective in achieving high-rate production of dry powder spray dried products, with substantially reduced capital equipment costs, energy requirements, and operating expenditures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part under 35 USC § 120 of U.S. patentapplication Ser. No. 16/055,075 filed Aug. 4, 2018 in the names ofCharles Pershing Beetz and Jason Andrew Beetz for ULTRAHIGH EFFICIENCYSPRAY DRYING APPARATUS AND PROCESS, now U.S. Pat. No. 10,252,181, whichin turn is a continuation-in-part under 35 USC § 120 of U.S. patentapplication Ser. No. 16/005,302 filed Jun. 11, 2018 in the names ofCharles Pershing Beetz and Jason Andrew Beetz for ULTRAHIGH EFFICIENCYSPRAY DRYING APPARATUS AND PROCESS, now U.S. Pat. No. 10,155,234, whichin turn is a continuation-in-part under 35 USC § 120 of U.S. patentapplication Ser. No. 15/865,657 filed Jan. 9, 2018 in the names ofCharles Pershing Beetz and Jason Andrew Beetz for ULTRAHIGH EFFICIENCYSPRAY DRYING APPARATUS AND PROCESS, now U.S. Pat. No. 9,993,787, whichin turn is a continuation-in-part under 35 USC § 120 of U.S. patentapplication Ser. No. 15/668,832 filed Aug. 4, 2017 in the names ofCharles Pershing Beetz and Jason Andrew Beetz for ULTRAHIGH EFFICIENCYSPRAY DRYING APPARATUS AND PROCESS, now U.S. Pat. No. 9,861,945. Thedisclosures of U.S. patent application Ser. Nos. 16/055,075, 16/005,302,15/865,657 and 15/668,832 are hereby incorporated herein by reference,in their respective entireties, for all purposes.

BACKGROUND Field of the Disclosure

The disclosure relates to ultrahigh efficiency spray drying apparatusand process, utilizing induction of localized turbulence in a dryingfluid flow stream to produce spray dried product, having particularutility for low temperature spray drying operations in which thermallysensitive materials are spray dried.

Description of the Related Art

Spray drying has existed as a basic materials processing operation sincethe late 1800s, and has been continually refined since that time. Thespray drying operation may be of varied character, but typicallyinvolves injecting a liquid composition of material into a chamber forcontact with a drying fluid concurrently flowed through the chamber. Theinjected wet material in the form of droplets contacts the stream ofdrying fluid so that the liquid passes from the droplets to the dryingfluid stream, producing a spray dried product that is discharged fromthe drying chamber, and drying fluid effluent that likewise isdischarged from the drying chamber.

In prior spray drying operations, it has been conventional practice toprovide the drying fluid as a gas at high elevated temperature, e.g.,temperatures on the order of 180-200° C., in order to produce dry powderproducts. The drying fluid has conventionally been air, and the materialto be spray dried may be provided in a dryable liquid form, e.g., as aneat liquid material, or the material may be a solid in a spray dryingliquid composition of slurry, suspension, emulsion, or solution form,which may additionally include carrier material with which the spraydried product is associated at the conclusion of the spray dryingprocess. In various applications, the material to be spray dried ispresent in a slurry containing solvent, e.g., water, alcohol, or otherappropriate liquid, as well as a carrier material, such as carbohydrate,cellulosic, wax, gum, protein, or other suitable material. To effect thespray drying operation, the spray drying composition is injected intothe drying chamber using a nozzle, atomizer, or the like, to form aspray of fine droplets for contacting with the drying fluid that isflowed into and through the drying chamber.

The aforementioned high elevated temperature levels on the order of180-200° C. for the drying fluid have been conventional practice in theart, in order to rapidly heat the droplets of spray dried material andvolatilize the liquid therefrom for production of spray dried powder.Such high temperature levels, however, limit the applicability of thespray drying operation to spray dryable materials that are thermallystable or otherwise are not severely adversely affected at the hightemperatures of the spray drying operation. A wide variety of materialscan accommodate the high temperature regime of the spray dryingoperation, but suffer losses of material (through volatilization of theproduct material at high temperature) and/or otherwise are degraded inphysical properties and/or performance characteristics as a result oftheir high temperature exposure during the spray drying operation. Insuch respect, the conventional spray drying practice has recognizedlimitations and deficiencies.

Against the foregoing context, the low temperature spray dryingapparatus and process disclosed in ZoomEssence, Inc.'s U.S. Pat. Nos.8,939,388, 9,332,776, and 9,551,527 embody a substantial advance in theart. As disclosed in such patents, spray drying is carried out at spraydrying conditions including inlet temperature of the drying fluid below100° C., and even down to ambient temperature in some applications,utilizing spray drying slurries having viscosity above about 300mPa-sec, slurry water content not exceeding 50% by weight of the slurry,and low humidity of the drying fluid introduced to the drying system.Such spray drying operation, conducted at low temperature spray dryingconditions markedly different from the conventional practice of the art,enables spray drying to be utilized for a myriad of products that wouldotherwise be contraindicated by the elevated temperature conditions ofconventional high temperature spray drying practice.

Nonetheless, even though the low temperature processing disclosed in theaforementioned U.S. patents of ZoomEssence, Inc. vastly expands thepopulation of spray dryable materials, large-volume spray dryingchambers are required to provide sufficient contact time between thedrying fluid and the sprayed droplets so that a dried powder product canbe achieved. In this respect, the lower temperature regime that isemployed in the ZoomEssence spray-drying process, relative toconventional high temperature spray drying, provides correspondinglyreduced thermal driving force for volatilization of liquid from thedroplets of the material being spray dried, and significant residencetime of the sprayed droplets and corresponding extent of drying chambervolume therefore are needed to accommodate lower temperature of thedrying fluid in the spray drying operation.

Large-volume spray drying chambers entail substantial capital equipmentand operating costs, and require correspondingly sized atomizers,nozzles, pumps, compressors, piping, valving, and ancillary processequipment. This is true of spray drying systems generally, regardless ofwhether conventional high temperature spray drying, or the lowtemperature spray drying process of the aforementioned ZoomEssencepatents, is practiced.

Accordingly, it would be a major advance in the art to provide a spraydrying system and process in which spray drying can be carried out atultrahigh hydrodynamic efficiency, enabling dramatically smaller spraydrying vessels and dramatically shorter residence times to be utilizedto produce spray dried powder product

Such ultrahigh efficiency spray drying would thus enable a spray dryingsystem of very compact, small footprint, character to be achieved,regardless of operating temperature regime, but when deployed in the lowtemperature operation described in the aforementioned ZoomEssence U.S.patents, would be remarkably effective in achieving high-rate productionof dry powder spray dried products with substantially reduced capitalequipment costs, energy requirements, and operating expenditures.

SUMMARY

The present disclosure relates to spray drying apparatus and processenabling spray drying operation to be conducted with ultrahighefficiency, particularly when low temperature operation of the typedescribed in ZoomEssence, Inc.'s U.S. Pat. Nos. 8,939,388, 9,332,776,and 9,551,527 is carried out. The disclosures of such U.S. Pat. Nos.8,939,388, 9,332,776, and 9,551,527 are hereby incorporated herein byreference, in their respective entireties, for all purposes.

In one aspect, the present disclosure relates to a method of processinga spray dryable liquid composition to form a spray dried product, saidmethod comprising:

generating a spray of the spray dryable liquid composition;

contacting the spray of spray dryable liquid composition in a spraydrying contact zone with a stream of primary drying fluid;

injecting pressurized secondary drying fluid into the stream of primarydrying fluid in the spray drying contact zone at multiple loci thereofto provide localized turbulence at said multiple loci; and

recovering the spray dried product from the spray drying contact zone.

In another aspect, the disclosure relates to a spray drying system,comprising:

a spray drying vessel including an interior volume for contacting ofintroduced spray dryable liquid composition and a stream of primarydrying fluid, said vessel including a spraying device positioned tointroduce a spray of the spray dryable liquid composition into theinterior volume for said contacting, an inlet for introduction of theprimary drying fluid to the interior volume, and an outlet fordischarging spray dried product and effluent drying fluid from theinterior volume; and

a multiplicity of secondary fluid injectors constructed and arranged tointroduce pressurized secondary drying fluid into the interior volume atflow conditions providing localized turbulence in the stream of primarydrying fluid in the interior volume at multiple loci in the stream ofprimary drying fluid.

In another aspect, the disclosure relates to a spray drying apparatus,comprising: a spray drying chamber having an interior volume andconfigured for introduction of spray dryable material into the interiorvolume for drying therein, and discharge of dried material and dryingfluid therefrom; a primary drying fluid inlet arranged to introduceprimary drying fluid into the interior volume of the chamber for contactwith the spray dryable material in the interior volume, to provide aprimary drying fluid flow stream through the interior volume; and amultiplicity of secondary drying fluid inlets configured tointermittently inject secondary drying fluid into the primary dryingfluid flow stream to effect transient localized turbulence in theprimary drying fluid flow stream, or alternatively for continuousinjection of secondary drying fluid into the primary drying fluid flowstream, for enhancement of drying of the spray dryable material in theinterior volume of the chamber.

Another aspect of the disclosure relates to a spray drying systemcomprising a spray drying apparatus of any of the types described above.

In a further aspect, the disclosure relates to a method of spray dryingof a spray dryable material, comprising use of apparatus of any of thetypes described above.

In a further aspect, the disclosure relates to a method of spray dryingof a spray dryable material in a primary drying fluid flow stream,comprising injecting secondary drying fluid into the primary dryingfluid flow stream at multiple loci in the primary drying fluid flowstream, so as to create localized turbulence at such loci that enhancesdrying of the spray dryable material.

In a still further aspect, the disclosure relates to a method of spraydrying of a spray dryable material in a primary drying fluid flowstream, comprising intermittently, transiently, and cyclically injectingsecondary drying fluid into the primary drying fluid flow stream atmultiple loci in the primary drying fluid flow stream, so as to createtransient localized turbulence at such loci that enhances drying of thespray dryable material, or alternatively, continuously injectingsecondary drying fluid into the primary drying fluid flow stream atmultiple loci in the primary drying fluid flow stream, so as to createlocalized turbulence at such loci that enhances drying of the spraydryable material.

Another aspect of the present disclosure relates to a spray dryingsystem, comprising:

(a) a spray drying vessel comprising:

-   -   (i) an interior volume arranged to receive an atomized        spray-dryable material and drying fluid for contacting of the        atomized spray-dryable material with the drying fluid in the        interior volume;    -   (ii) at least one drying fluid inlet by which the drying fluid        is introduced into the interior volume for said contacting; and    -   (iii) a spray-dried material outlet communicating with the        interior volume, arranged to discharge spray-dried material and        effluent drying fluid from the vessel;

(b) an atomizer adapted to receive a spray-dryable material anddischarge the atomized spray-dryable material into the interior volumeof the vessel for said contacting;

(c) at least one turbulator adapted to generate turbulence in the dryingfluid in the interior volume of the vessel;

(d) a process control unit adapted to regulate flow rate of drying fluidinto the interior volume and flow rate of the spray-dryable material tothe atomizer so that interaction of the drying fluid with the at leastone turbulator produces turbulence in the drying fluid having aKolmogorov length less than average particle size of spray-dryablematerial droplets in the atomized spray-dryable material in the interiorvolume of the vessel.

A further aspect of the present disclosure relates to a process forproducing a spray-dried material, comprising:

generating an atomized spray-dryable material;

contacting the atomized spray-dryable material with drying fluid to formspray-dried material;

recovering the spray-dried material from the drying fluid; and

during said contacting, inducing turbulence in the drying fluid having aKolmogorov length less than average particle size of spray-dryablematerial droplets in the atomized spray-dryable material.

In another aspect, the disclosure relates to a spray drying system,comprising:

(a) a spray drying vessel comprising:

-   -   (i) an interior volume arranged to receive an atomized        spray-dryable material and drying fluid for contacting of the        atomized spray-dryable material with the drying fluid in the        interior volume;    -   (ii) at least one drying fluid inlet by which the drying fluid        is introduced into the interior volume for said contacting; and    -   (iii) a spray-dried material outlet communicating with the        interior volume, arranged to discharge spray-dried material and        effluent drying fluid from the vessel;

(b) an atomizer adapted to receive a spray-dryable material anddischarge the atomized spray-dryable material into the interior volumeof the vessel for said contacting;

(c) at least one turbulator adapted to generate turbulence in the dryingfluid in the interior volume of the vessel;

(d) a process control unit adapted to regulate flow rate of drying fluidinto the interior volume and flow rate of the spray-dryable material tothe atomizer so that interaction of the drying fluid with the at leastone turbulator produces turbulence in the drying fluid producing aturbulence dissipation rate exceeding 25 m²/sec³.

A further aspect of the disclosure relates to a process for producing aspray-dried material, comprising:

generating an atomized spray-dryable material;

contacting the atomized spray-dryable material with drying fluid to formspray-dried material;

recovering the spray-dried material from the drying fluid; and

during said contacting, inducing turbulence in the drying fluidproducing a turbulence dissipation rate exceeding 25 m²/sec³.

The present disclosure in yet another aspect relates to a spray dryingsystem, comprising:

(a) a spray drying vessel comprising:

-   -   (i) an interior volume arranged to receive an atomized        spray-dryable material and drying fluid for contacting of the        atomized spray-dryable material with the drying fluid in the        interior volume;    -   (ii) at least one drying fluid inlet by which the drying fluid        is introduced into the interior volume for said contacting; and    -   (iii) a spray-dried material outlet communicating with the        interior volume, arranged to discharge spray-dried material and        effluent drying fluid from the vessel;

(b) an atomizer adapted to receive a spray-dryable material anddischarge the atomized spray-dryable material into the interior volumeof the vessel for said contacting;

(c) turbulators positioned to generate localized turbulence in thedrying fluid throughout the interior volume of the vessel; and

(d) a process control unit adapted to regulate flow rate of drying fluidinto the interior volume and flow rate of the spray-dryable material tothe atomizer so that interaction of the drying fluid with theturbulators produces localized turbulence in the drying fluid throughoutthe interior volume of the vessel.

Another aspect of the present disclosure relates to a process forproducing a spray-dried material, comprising:

generating an atomized spray-dryable material;

contacting the atomized spray-dryable material with drying fluid to formspray-dried material;

recovering the spray-dried material from the drying fluid; and

during said contacting, inducing localized turbulence throughout saiddrying fluid engaged in said contacting.

Other aspects, features and embodiments of the disclosure will be morefully apparent from the ensuing description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 is a schematic representation of a spray drying process systemaccording to one embodiment of the present disclosure.

FIG. 2 is a schematic representation, in breakaway view, of a portion ofthe spray drying process system of FIG. 1, showing the action oflocalized turbulence induction in the spray drying vessel of the system.

FIG. 3 is a graphical depiction of particle trajectories in a tangentialinlet rotary atomizer spray dryer, as calculated using computationalfluid dynamics, illustrating the movement of the particles to the outerwall of the dryer, leaving a substantial volume that is devoid ofparticles.

FIG. 4 is a graphical depiction of a computational fluid dynamicssimulation of effect on total diffusivity caused by turbulent puffsintroduced into airflow in a rectangular duct, 1.5 seconds after thepuff has occurred.

FIG. 5 is a schematic representation of a spray drying apparatusaccording to one embodiment of the present disclosure, featuring anarray of turbulent mixing nozzles on the spray drying chamber wall,configured for injection of transient, intermittent turbulent air burstsinto the main fluid flow in the spray drying chamber.

FIG. 6 is a scanning electron microscope (SEM) image of a cross sectionof a particle produced by low temperature spray drying, asrepresentative of dry powder product produced in accordance with themethods and apparatus of the present disclosure.

FIG. 7 is a depiction of drying fluid stream lines in a spray dryingvessel in which a main flow of drying fluid is introduced at an upperportion of the vessel, with additional drying fluid being introduced formaintenance of a fluidized bed in a lower portion of the spray dryingvessel, and with spray drying fluid being discharged from dischargeports at an upper and outer portion of the spray drying vessel.

FIG. 8 is a depiction of particle trajectories in a spray drying vesselof the type for which drying fluid stream lines are depicted in FIG. 7.

FIG. 9 is a schematic representation of a spray drying system accordingto another embodiment of the present disclosure, featuring an array offluid injector jets on the spray drying vessel wall to enhance spraydrying efficiency of the system.

FIG. 10 is a schematic representation of a spray drying process systemaccording to a further embodiment of the present disclosure.

FIG. 11 is a graph of turbulent dissipation rate, in m²/sec³, as afunction of radial distance in an interior volume of a spray dryingvessel, at different vertical heights in such interior volume, for afirst illustrative spray drying system (Dryer 1).

FIG. 12 is a graph of turbulent dissipation rate, in m²/see, as afunction of radial distance in an interior volume of a spray dryingvessel, at different vertical heights in such interior volume, for asecond illustrative spray drying system (Dryer 2).

FIG. 13 is a schematic representation of a spray drying system accordingto a further embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure relates to a spray drying apparatus and processin which localized turbulence is induced in the drying fluid flow streamto enhance the production of spray dried product in an ultrahighlyefficient manner, particularly when low temperature spray drying iscarried out.

In conventional high-temperature spray drying installations, in whichdrying fluid is supplied to the spray drying vessel at temperatures onthe order of 180° C.-200° C., the present inventors have determined thatindependently of energy efficiency as commonly measured in the spraydrying industry, the actual utilization of the drying capacity of thedrying fluid (dry air) that is supplied to the spray drying vessel incommercial operations is only about 10% to 50%. Such inefficiency of thedrying capacity of the drying fluid manifests itself in increasedresidual moisture concentrations in the spray dried powder product or asdeposition of sticky powder on the walls of the spray dryer vessel. Suchinefficiency is generally accommodated by operating at the highestpossible drying temperatures and/or utilizing secondary post-spraydrying processes such as in-line fluidized bed drying. These secondarydrying processes add to the complexity, cost and decreased energyefficiency of the overall spray drying process system.

As indicated in the discussion in the Background section hereof, thehigh elevated temperature levels on the order of 180° C.-200° C. thatare utilized in conventional spray drying practice are recognized assignificantly limiting the types of materials that may be processed byspray drying and as entailing significant detriment to the spray driedproduct, with respect to volatilization losses of product material,promotion of unwanted degradative and decomposition chemical reactions,and reduction of shelf life and stability characteristics, as well asincreased capital, energy, and operating costs associated with the hightemperature operation.

As also discussed in the background section hereof, the low temperaturespray drying apparatus and process disclosed in ZoomEssence, Inc.'s U.S.Pat. Nos. 8,939,388, 9,332,776, and 9,551,527 embody a substantialadvance in the art, permitting spray drying to be carried out at spraydrying conditions including inlet temperature of the drying fluid below100° C., and even down to ambient temperature in some applications,utilizing spray drying slurries having viscosity above about 300mPa-sec, slurry solvent (e.g., water) content not exceeding 50% byweight of the slurry, and low humidity of the drying fluid introduced tothe drying system.

The invention of the present disclosure represents a further advance inthe art that is applicable to both conventional spray drying operationsconducted at high elevated temperature levels, as well as to(electrostatic spray drying as well as non-electrostatic spray drying)low temperature spray drying operations conducted in accordance with thedisclosures of the aforementioned ZoomEssence patents, in enabling suchsystems to achieve ultrahigh efficiency in the spray drying operationsby induction of localized turbulences in the flow stream of drying fluidthat is passed through the spray drying vessel. Such induction oflocalized turbulences enables extraordinarily high levels of masstransfer of solvent from the spray dried droplets to the drying fluid inthe spray drying operation, enabling minimal spray drying vessel volumesto be utilized for achievement of spray dried powder products, therebyachieving capital equipment, energy, and operating expense reductions ofa surprising and unexpected character. Such advantages are particularlysubstantial in low temperature spray drying operations, and enableremarkably compact and efficient spray drying process systems to beefficiently utilized in high rate commercial spray drying operations.

While the disclosure herein is primarily directed to the use of air as adrying fluid in the spray drying apparatus and method of the disclosure,it will be recognized that other drying fluids may be employed, asspecific to the apparatus and methodology involved. For example, thedrying fluid may comprise oxygen, oxygen-enriched air, nitrogen, helium,argon, neon, carbon dioxide, carbon monoxide, or other fluid species,including single component fluids, as well as fluid mixtures. The dryingfluid may in various applications exist in a gaseous or vapor form, andthe fluid should be constituted to provide an appropriate mass transferdriving force for passage of solvent or other desirably volatilizablematerial from the spray of spray dried material to the drying fluid.

The spray drying apparatus and process of the present disclosure may beutilized for spray drying of any suitable material that is spray dryableto constitute a desired product. The spray dried material may forexample comprise a food material, beverage material, fragrance material,pigment material, flavor material, pharmaceutical material, therapeuticmaterial, medication material, homeopathic material, biologicalmaterial, probiotic material, construction material, formulatingmaterial, as well as any other materials that are spray dryable, andincluding mixtures, blends, composites, and combinations of two or moredifferent materials of such types.

The spray dryable material may be of an initially liquid form that isspray dried to effect drying thereof to form a dry product.Alternatively, the spray dryable material may be of a solid or semisolid form, which is combined with other ingredients to form a spraydryable composition, e.g., ingredients selected from among solvents,carriers, adjuvants, excipients, surfactants, anti-agglomerants,anti-caking agents, co-active ingredients, wetting agents, dispersants,emulsifiers, stabilizers, antioxidants, preservatives, encapsulants,pore-forming agents, hardeners, including mixtures, blends, composites,and combinations of two or more ingredients of such types.

Solvents used in the spray dryable compositions of the presentdisclosure may be of any suitable type and may for example includewater, inorganic solvents, organic solvents, and mixtures, blends,emulsions, suspensions, and solutions thereof. In various embodiments,organic solvents may be employed, such as for example acetone,chloroform, methanol, methylene chloride, ethanol, dimethyl formamide(DMF), dimethyl sulfoxide (DMS), glycerine, ethyl acetate, n-butylacetate, and mixtures with water of the one or more of the foregoing.Such organic solvents may for example be used in spray drying of spraydryable compositions including protein-based materials. In specificembodiments, solvent selected from the group consisting of water,alcohols, and water-alcohol solutions may be advantageously employed.

In various applications, the spray dryable material will be solidmaterial that is formulated with solvent and carrier material to form aspray dryable emulsion or slurry composition, in which the solvent isremoved from the finely divided droplets of spray dried material in thespray drying operation and the product material then is associated withthe carrier material in the dry powder product. The carrier material maybe of any suitable type, and may for example be selected from amongcarbohydrates, proteins, lipids, waxes, cellulosic material, sugars,starches, natural and synthetic polymeric materials, and any othermaterials having utility in association with the product material in thespray dried powder product. The carrier in some applications may be anencapsulant material, so that the spray dried powder product includesthe product material encapsulated within the carrier material.Alternatively, the carrier may simply be associated with the productmaterial in the spray dried powder product, e.g., as a substrate,support, or associative matrix for the product material. Among preferredcarriers used in spray dryable liquid compositions in the spray dryingsystems and processes of the present disclosure, are starch carriers,sugar carriers, and cellulosic carriers.

Thus, the spray dryable compositions utilized in the systems andprocesses of the present disclosure may be of any suitable type, and mayin specific embodiments comprise slurries or emulsions, or otherwise beconstituted as solid dispersions.

In various low temperature (temperature of drying fluid fed to the spraydrying vessel <100° C.) applications, when the spray dryable liquidcomposition comprises a slurry or emulsion of carrier, product material,and solvent, the viscosity of the slurry material may be controlled byappropriate formulations so that at the time of spray drying of theliquid composition, the viscosity is advantageously in a range of from300 mPa-s (1 mPa-s=1 centipoise) to 28,000 mPa-s or more. In variousother applications, the viscosity may be in a range in which a lowerlimit of the range is any one of 325, 340, 350, 375, 400, 450, 500, 550,600, 650, 700, 750, 800, 850, 900, 950, and 1000 mPa-s, and in which anupper limit of the range is greater than the lower limit and is any oneof 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000,2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10,000, 11,000, 12,000,13,000, 14,000, 15,000, 16,000, 17,000, 18,000, 19,000, and 20,000, withany viscosity ranges comprising any one of such lower limits and any oneof such upper limits being usefully employed in various specificapplications. A preferred viscosity range in some applications is from500 to 16,000 mPa-s, and a preferred viscosity range in otherapplications is from 1000 to 4000 mPa-s.

In various low temperature applications involving spray dryable liquidcompositions in the form of slurries or emulsions of carrier, productmaterial, and solvent, the ratio of solvent within the slurry oremulsion is desirably controlled so that the amount of solvent withinthe slurry at the spray drying operation does not exceed 50% by weight,based on total weight of the slurry (emulsion). For example, in variousapplications, the amount of solvent in the slurry at the spray dryingstep may be from 20 to 50 weight percent, or from 20 to 45 weightpercent, or from 20 to 40 weight percent, or from 25 to 35 weightpercent, on the same total weight basis, as appropriate to the specificspray drying operation and materials involved.

The temperature of the drying fluid introduced to the spray dryingvessel in the low temperature spray drying operations of the presentdisclosure may be any suitable temperature below 100° C., as measured atthe inlet of the spray drying vessel (typically referred to in the artas the inlet temperature of the drying fluid). In various applications,the inlet temperature of the drying fluid may be controlled to be below95° C., 90° C., 85° C., 80° C., 75° C., 70° C., 65° C., 60° C., 55° C.,50° C., 45° C., 40° C., 35° C., 30° C., 25° C., or 20° C., asappropriate to the specific spray drying operation involved.

In other applications, in which the apparatus and method of the presentdisclosure are utilized in conventional high-temperature spray drying(temperature of drying fluid fed to the spray drying vessel on the orderof 180-200° C. or more), the spray dryable liquid composition containingcarrier, product material, and solvent may have viscosity between about10 and 200 mPa-s, and may contain an amount of water of from 50 to 70%by weight, based on total weight of the slurry (emulsion).

In still other applications, the temperature of the drying fluid fed tothe spray drying vessel may be in an intermediate temperature regime,with an inlet temperature in a range of from 100° C. to 180° C. Invarious embodiments, the inlet temperature of the drying fluid may becontrolled to be below 180° C., 175° C., 170° C., 165° C., 160° C., 155°C., 150° C., 145° C., 140° C., 135° C., 130° C., 125° C., 120° C., 115°C., 110° C., or 105° C., or otherwise in a range whose upper limit maybe any of the preceding specific temperatures, and whose lower limit isany one of the preceding temperatures below the upper limit temperature,or 100° C.

In yet other applications, the temperature of the drying fluid fed tothe spray drying vessel may be below at least one of 120° C., 115° C.,110° C., 100° C., 95° C., 90° C., 85° C., 80° C., 75° C., 70° C., 65°C., 60° C., 55° C., 50° C., 45° C., 40° C., 35° C., 30° C., 25° C., and20° C., and above freezing temperature of liquid to be volatilized forspray drying of the spray-dryable material.

It will be appreciated that the viscosity and solvent concentration maybe widely varied in specific applications, depending on the temperatureregime and other spray drying operation conditions and materials. Ingeneral, the low temperature (electrostatic or alternativelynon-electrostatic) spray drying methodology of the aforementionedZoomEssence patents is preferred in the practice of the presentdisclosure, since such low temperature spray drying methodology utilizesless solvent (water) in the slurry or emulsion that is spray dried,which in turn greatly enhances drying at low temperatures sincesubstantially less solvent is required to be evaporated in the spraydrying operation. In marked contrast to high temperature drying, the“constant” rate period in low temperature spray drying is very short ornonexistent due to the initial low solvent concentration of the slurryor emulsion, so that drying is controlled almost from the outset bydiffusion from the inner particle core through a porous drying layer toproduce fully dense dry powder product without hollow regions or shellstructures. The low temperature process in the localized turbulencegeneration method and apparatus of the present disclosure achieves ahigh concentration gradient between the sprayed particle (droplet)surface and the surrounding drying fluid.

The spray dried powder material that is produced by the spray dryingapparatus and method of the present disclosure may be in any suitablemorphological and physical forms, including spherical, spheroidal,polygonal, cuboidal, rod, fiber, helical, dendritic, and any otherspatial forms, and may be of any suitable particle size distributionappropriate to the spray dried powder product.

The drying fluid in the spray drying process of the present disclosurein many applications may be or comprise air, and the solvent in thespray dryable liquid composition may be water or other aqueous medium,e.g., a water-alcohol solution. It is generally desirable that thedrying fluid in the spray drying process be as dry as possible, in orderto maximize the mass transfer gradient for transfer of solvent from thespray dried droplets to the drying fluid. In practice, this may involvetreatment of the drying fluid to effect condensation of any moisture orother condensable material in the drying fluid, so that it is removedfrom the fluid stream that is flowed to the spray drying vessel fordrying of the spray liquid composition in the interior volume of suchvessel. In other applications, the treatment of the drying fluid mayinvolve contacting of such fluid with physical adsorbent and/or chemicaladsorbent materials, to remove components of the fluid that may beadverse to the drying process.

For such purpose, the spray drying system and process of the presentdisclosure may utilize a dehumidification assembly to provide dryingfluid at a predetermined relative humidity level. For example, thedehumidification assembly may be constructed and arranged, andcontrollably operated, to provide drying fluid to the spray dryingvessel at a relative humidity not exceeding 35%, 30%, 25%, 20%, 15%,12%, 10%, 8%, 6%, 5%, 4%, 3%, 2.5%, 2%, 1.8%, 1.6%, 1.5%, 1.4%, 1.3%,1.2%, 1.1%, 1.0%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%,0.05%, 0.02%, or 0.01%. In other embodiments, the dehumidificationassembly may be constructed and arranged to provide drying fluid at arelative humidity in a range in which the lower end point of the rangeis any one of 10⁻⁴%, 10⁻³%, 10⁻²%, 10⁻¹%, 1%, 1.5%, or 2%, and in whichthe upper end point of the range is greater than the lower end point ofthe range, and is any one of 35%, 30%, 25%, 20%, 15%, 12%, 10%, 8%, 6%,5%, 4%, 3%, 2.5%, 2%, 1.8%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1.0%,0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.05%, 0.02%,0.01%, or 0.05%. In still other embodiments, the dehumidificationassembly may be constituted to provide the drying fluid at a relativehumidity in a range of 10⁻⁴% to 35%, 10⁻³% to 18%, 0.005 to 17%, 0.01%to 15%, 0.01 to 5%, 0.1 to 5%, or 0.001% to 2%.

In various applications in which the drying fluid is or comprises air,and the spray dryable liquid composition is an aqueous composition, itis advantageous to control the relative humidity of the drying fluid, sothat it is below 20% relative humidity, preferably below at least one of18%, 15%, 12%, 10%, 8%, 5%, 2.5%, 2%, 1.5%, 1% and 0.5% relativehumidity.

Spray drying of the spray dryable liquid composition may be carried outin any suitable manner that effects a spray of the liquid composition inthe form of droplets or finely divided liquid particles, to provideappropriate surface to volume characteristics for the spray dryingoperation. The generation of the spray of spray dryable liquidcomposition may be effected with any suitable apparatus, includingatomizers, nebulizers, ultrasonic dispersers, centrifugal devices,nozzles, or other appropriate devices. The liquid composition may beintroduced into the interior volume of the spray drying vessel in aliquid film or ligament form that is broken up to form droplets. A widevariety of equipment and techniques is able to be utilized to form thespray of liquid composition in the form of droplets or finely dividedliquid particles. Typically, droplet size and distribution may be fairlyconstant for a given spray drying technique, and may be in a range of10-300 μm, or other suitable range.

Spray drying in accordance with the present disclosure may be orcomprise electrostatic spray drying, in which an electrostatic charge isapplied to the spray dryable feedstock liquid composition and/or to thewet particles produced by spraying of the feedstock liquid (e.g.,slurry) composition so that a spray of electrostatically charged, wetparticles (droplets) is produced, for enhanced drying of the particlesas a result of the electrostatic effects. Thus, electrostatic chargingof the spray-dryable material may be carried out before, during, orafter atomization of the feedstock material. Electrostatic sprayingequipment of widely varying types may be utilized in electrostaticspraying systems and operations in accordance with the presentdisclosure, e.g., an electrostatic spraying device positioned tointroduce an electrostatically charged spray of the spray dryable liquidcomposition into the interior volume of a spray drying vessel forcontacting with drying fluid therein, with induction of localizedturbulence in the spray drying vessel, in accordance with the presentdisclosure.

Thus, when spray drying in accordance with the present disclosurecomprises electrostatic spraying drying, the spray of the feedstockliquid composition is generated wherein the spray particles (droplets)advantageously have suitable electrostatic charge to enhance the spraydrying operation, in relation to a corresponding spray drying operationin which electrostatic spray drying is not conducted. For example, anelectrostatic spray atomizer may be employed to apply an electrostaticcharge to the sprayed particles that is in a range of from 0.25 kV to 80kV, although it will be recognized that higher or lower electrostaticcharge may be imparted to the material to be spray dried in specificapplications. In various embodiments, electrostatic charge imparted tothe particles being spray dried may be in a range of from 0.5 to 75 kV,or from 5 to 60 kV, or from 10 to 50 kV, or in other suitable range orother specific value.

In other embodiments of electrostatic spray drying conducted inaccordance with the present disclosure, the feedstock liquid compositionmay be sprayed through an electrostatic nozzle operatively coupled witha voltage source arranged to apply a cyclically switched voltage to thenozzle, e.g., between high and low voltages that are within any of theabove-discussed, or other, voltage ranges.

In accordance with the present disclosure, localized turbulence isgenerated in the fluid stream of drying fluid flowed through the dryingchamber of the spray drying vessel, intermittently or alternativelycontinuously, to provide perturbations in the overall drying fluid flowstream to enhance mass transfer efficiency of the drying operation, inthe contact of the drying fluid with the sprayed liquid. The inductionof localized turbulence in the drying fluid flow stream may be effectedin any suitable manner, and may for example be generated by providing amultiplicity of jets or injectors that provide an intermittent orsustained burst of fluid into the drying fluid flow stream to inducelocalized turbulence in the flow stream, thereby disrupting any stagnantfilms of fluid on the sprayed liquid droplets or particles and effectinga local renewal of surface exposure of the liquid droplets or particles,in contact with the drying fluid flow stream.

For the induction of localized turbulence in the drying fluid flowstream, an array of jets or injectors may be arranged in and/or on thespray drying vessel, which inject secondary streams of fluid in adirectional manner effecting the creation of localized turbulence. Thearray may be provided in a geometrically regular or irregulararrangement, and the jets or injectors may be oriented so that thedirection of injection of secondary fluid into the main drying fluidflow stream is transverse to the bulk flow direction of the main dryingfluid flow stream, or oblique in relation to such bulk flow direction,or otherwise oriented to generate the requisite localized turbulenceactivity in the drying fluid flow stream. The fluid utilized for suchinduction of localized turbulence may be of any suitable fluid type, andmay for example be of a same fluid type as the main drying fluid flowstream, or alternatively may be of a different type that is compatiblewith the main drying fluid flow stream to effectuate enhancement of thedrying operation. The injection of secondary streams of fluid may invarious embodiments be carried out continuously, and in otherembodiments, such injection of secondary streams of fluid may be carriedout intermittently, e.g., cyclically and repetitively, as a burst orpuff of the secondary fluid into the main drying fluid flow stream.

For such purpose, the array of jets or injectors may be linked with oneanother by suitable piping, valving, and manifolding, to provide thesecondary fluid to the jets or injectors, e.g., from a common or unitarysecondary fluid source. The respective ones of the jets or injectors maylikewise be linked operationally by signal transmission lines to acontrol system so that the jets or injectors are actuated in anysuitable coordinated fashion. For example, each of the jets or injectorsmay be actuated on a same cycle time sequence, for simultaneoustransient injection of secondary fluid into the main drying fluid flowstream. Alternatively, the jets or injectors may be actuated so thatonly a portion thereof is actuated at a particular time, i.e., so thatrespective groups in the array are sequentially actuated, so that afirst set of jets or injectors in a specific location is actuated forinjection of secondary fluid into the main drying fluid flow stream,following which the first set of jets or injectors is shut off and asecond set of jets or injectors at another specific location is actuatedfor injection of secondary fluid into the main drying fluid flow stream,in alternating fashion, or as part of a larger sequence of third,fourth, etc. sets of jets or injectors, in which each set is transientlyactuated in turn, in the overall sequence.

Such array of jets or injectors may be of relatively simple character,involving only two, or several, jets or injectors that are concurrentlyor sequentially operated for secondary fluid introduction to the maindrying fluid flow stream, or the array may include numerous jets orinjectors, e.g., an array of from 5 to 100 jets or injectors, or evenmore, as appropriate to enhance the mass transfer of solvent from thesprayed liquid composition to the drying fluid flow stream in the spraydrying vessel. It will therefore be appreciated that any number of jetsor injectors can be utilized for localized induction of turbulence toenhance mass transfer in the spray drying operation, and that theoperation of such jets or injectors can be continuous or intermittent,and may be partially or wholly synchronized with respect to portions orparts of the overall array, or may be carried out in any of variousasynchronous manners, as appropriate to achieve enhancement of the spraydrying operation. It will therefore be appreciated that a control systemmay be operatively linked to the individual jets or injectors in thearray, wherein each of the jets or injectors is selectively actuated inan appropriate sequence and for a predetermined duration, by anassociated control system.

The control system may therefore comprise a central processing unit,microprocessor, microcontroller, general or special purpose programmablecomputer, programmable logic controller, or the like, which carries outa cycle timer program. The cycle timer program may be constituted totransmit actuation signals to specific ones of the multiplicity of jetsor injectors in the array according to a predetermined sequence ofactuation for the jets or injectors in the array, so that the jets orinjectors discharge pressurized secondary gas into the main drying fluidflow stream in such predetermined sequence. For such purpose, thecentral processing unit (CPU) or other controller may transmit actuationsignals to the respective jets or injectors in the array according tothe sequence to be carried out, wherein such actuation signals may forexample open valves in the jets or injectors to provide for flow ofpressurized gas through the jets or injectors and into the main dryingfluid flow stream, with corresponding deactuation signals being sent tothe respective jets or injectors in the array to close the valves in thejets or injectors to provide for termination of flow of pressurized gastherethrough into the main drying fluid flow stream. The valves may bedeployed in the jets or injectors themselves or may be associated withsuch jets or injectors, e.g., in a manifold flow circuitry that iscoupled with the jets or injectors in the array.

In general, the size, shape, number, and arrangement of the jets orinjectors in the array may be widely varied to achieve optimumgeneration of localized turbulence that in turn maximizes the dryingrate for the spray drying vessel, to produce dried powder product. Inthis respect, specific arrangements may be determined by hydrodynamicmodeling of the main drying fluid flow stream and introductions ofpressurized secondary fluid therein, to develop specific arrays ofsuitable size, shape, number, and arrangements of the jets or injectors.Alternatively and/or additionally, the size, shape, number, andplacement of the jets or injectors may be determined by empiricalmethods, utilizing injection of pressurized secondary fluid containingtracer die therein, together with high-speed imaging of the fluid flowstream in the spray drying chamber, and empirical measurement oflocalized Reynolds numbers and other hydrodynamic variables, toexperimentally determine an advantageous size, shape, number, andarrangements of jets or injectors in the array.

The spray drying vessel that is utilized in the practice of the presentdisclosure may be of any suitable size, shape, and arrangement, it beingunderstood that the localized turbulence generation mediated byinjection of secondary fluid by jets or injectors achieves a substantialimprovement in drying efficiency of the spray drying vessel, relative tothe drying efficiency that would be realized in the absence of suchlocalized turbulence generation. Such improvement enables the spraydrying vessel to be of a smaller volumetric character than would berequired in the absence of such localized turbulence generation.Accordingly, the apparatus and method of the present disclosurefacilitates the utilization of smaller, more compact spray dryingvessels than are conventionally employed, so that the footprint of thespray dryer and overall process system can be made substantiallysmaller, with the increased drying efficiency providing benefits inrespect of capital equipment, energy, and operating costs of the spraydrying process system.

As an aid in understanding the improvement achieved by the apparatus andmethod of the present disclosure, it is instructive to consider thehydrodynamic character of a conventional spray drying vessel. A typicalspray drying vessel geometry in conventional high-temperature spraydrying operation involves a tall cylindrical tank that is supplied witha source of heated dry air. Once the air enters the spray dryer, theturbulent flow of the heated drying fluid quickly exchanges heat andmass with the atomized particles of the sprayed emulsion. The particleson leaving the atomizer are traveling at high speeds, which may be onthe order of 50 to 150 meters/second. The particles are quickly slowedby air drag effects and become entrained in the dryer air flow. As theparticles travel further from the atomizer and lose water (solvent) dueto evaporation, the airflow is progressively less turbulent and thewater concentration in the vicinity of the particle on average increasesdue to the limited diffusivity of water vapor in air. The particledrying rate is driven in part by the difference in water concentrationin the particle and that in the air immediately surrounding theparticle. Initially the concentration gradient is very large, and asevaporation from the particle surface progresses, the gradientdecreases, slowing the rate of evaporation and the drying process.

In the interior volume of a conventional spray drying vessel, there aretypically large regions where the particle density is low due to the air(drying fluid) flow patterns, and in which the air has a much lowerwater vapor concentration than other regions in which the drying fluidflow contains high concentrations of entrained particles. The result ofthese heterogeneities is that lower particle density regions ofsignificantly drier air do not become mixed with higher particle densityregions until the particles and associated fluid leave the spray dryingvessel, whereupon the respective regions finally become mixed. Thiseffluent from the spray drying vessel then typically passes to a cycloneor other fluid/solid separator device, and because the contact time fromthe spray drying vessel outlet to the cyclone apparatus is short, on theorder of a few seconds, the mixing effect is insignificant and the airleaves without being fully utilized.

Thus, in the interior volume of the spray drying vessel, the particledistribution is non-homogeneous, and the overall efficiency of the spraydrying operation is correspondingly reduced.

The present disclosure addresses these hydrodynamic inefficiencies ofthe conventional spray dryer systems, enhancing drying fluid utilizationby introducing puffs or jets of turbulent, dry secondary drying fluidalong the main drying fluid flow path of the spray drying chamber. Eventhough the drying fluid flow in conventional spray drying systems istypically turbulent at the point of introduction, with some extent ofassociated turbulent mixing being inherent, there are invariably flowstratification effects, wall effects, and hydrodynamic behavioralanomalies of the drying fluid in the spray drying chamber that produceinhomogeneities in the volumetric particle density in the spray dryingvessel during spray drying operation, resulting in low-level utilizationof the drying fluid.

The approach of the present disclosure, of utilizing turbulent air(drying fluid) puffs or jets to cause increased, widespread highintensity turbulent mixing throughout the spray drying vessel interiorvolume, avoids the adverse hydrodynamic effects and anomalies inherentin conventional spray drying operations, to enhance mixing of theparticle-laden, higher solvent concentration drying fluid flow regionswith particle-deficient, lower solvent concentration drying fluid flowregions, resulting in enhanced diffusivity of solvent and other liquidconstituents of the spray dried liquid composition in the interiorvolume of the spray drying vessel.

In various embodiments, the provision of localized turbulence in thedrying fluid throughout the interior volume of the spray drying vesselmay be accommodated by turbulators such as nozzles, jets, orifices, orother fluid introduction devices, which inject secondary drying fluidinto the interior volume of the spray drying vessel, as for example by amultiplicity of such devices arranged about the wall of the spray dryingvessel, a multiplicity of such devices in a central region of theinterior volume of the spray drying vessel, together with the provisionof primary drying fluid inlet(s) structure configured to provide arequisite level of localized turbulence in the drying fluid in the inletregion of the interior volume of the spray drying vessel. Secondarydrying fluid injection turbulators may be controllably operated by aprocess control unit of the spray drying system so that the turbulatorsand process control unit cooperatively provide localized turbulence ofthe drying fluid in the interior volume of the spray drying vessel witha predetermined turbulence intensity and turbulence dissipation rate,e.g., turbulence having a turbulence dissipation rate that exceeds 25m²/sec³.

In a spray drying process conducted in accordance with the presentdisclosure, wherein transient injection of pressurized secondary dryingfluid is effected, the transient jet or puff of drying fluid introducesa mass of turbulent dry fluid that moves through and mixes with the flowof particle-laden fluid circulating in the spray drying chamber. Theresulting turbulent region effected by such secondary fluid injectionalters the diffusion of molecular species in fundamental ways, and thehigh velocity flow produced by the jet or injector introduces chaoticflow behavior in which the molecular diffusion rate is substantiallyincreased. The turbulent diffusivity can be over an order of magnitudegreater than the diffusivity under non-turbulent conditions.Accordingly, particles in the turbulent regions created by the jets orinjectors will experience an increased drying rate due to the increaseddiffusivity of the localized turbulent regions. Such turbulence rapidlyreduces the concentration of solvent in the regions surrounding theparticles being dried, increasing concentration gradients and enablingsubstantially increased drying rates to be achieved. A further advantageof the turbulent puffers is accelerated cooling of the particles whenthe secondary fluid being injected is at low temperature, e.g., ambientor room temperature. Such temperature quenching effect is important whenmaterials being dried have a low glass transition temperature.

In various embodiments, the spray drying system utilized for carryingout the spray drying process of the present disclosure may be a “singlestep spray drying system”. As used herein, a “single step spray dryingsystem” refers to a spray drying system in which the spray dried powderproduct is produced solely by spray drying of spray-dryable material ina single spray drying vessel in which atomized particles of thespray-dryable material produced by a single source atomizer arecontacted with drying fluid to effect solvent removal from thespray-dryable material to a dryness of less than five weight percent ofsolvent, based on total weight of the spray-dried powder, without anypost-spray drying processing, e.g., fluidized bed treatment, coating, orchemical reaction. The “single source atomizer” specified in suchdefinition refers to a single atomizer that receives one spray-dryablematerial from a corresponding feed source, i.e., the atomizer does notconcurrently receive different spray-dryable materials from differentfeed sources.

The spray drying system in various embodiments of the present disclosuremay be constructed and arranged to produce highly dense spray-driedpowders of large particle size, as a result of the provision oflocalized turbulence in the drying fluid throughout the interior volumeof the corresponding spray drying vessel.

Spray dried powders produced in such spray drying systems of the presentdisclosure by spray drying processes conducted to provide localizedturbulence in the drying fluid throughout the interior volume of thecorresponding spray drying vessel may for example have (i) a ParticleSize Distribution in which at least 75% particles in the powder have aparticle size of at least 80 μm, (ii) a Particle Void Volume in theparticles of the powder that is less than 10% of the total particlevolume, and (iii) a Bulk Density of the particles of the powder that isin a range of from 22 to 40 pounds per cubic foot.

Such spray dried powder characteristics may be determined by thefollowing powder assessment procedures:

Particle Size Distribution is determined by measurement by a BeckmanCoulter LS 13 320 particle size analyzer providing a volumetricdistribution output, wherein approximately 1 gram of the spray driedpowder is loaded into a sample tube, and the Beckman Coulter LS 13 320particle size analyzer vacuums the powder through the analysis chamberaccording to the manufacturer's protocols, with laser diffraction datainterpreted via Fraunhofer method and reported as a volumetricdistribution, and particle size reported as the median value (d50) fromthe distribution.

Particle Void Volume is determined as a calculated percent of the volumetaken up by any air pockets inside a particle. The particle void volumemeasurement relies on a scanning electron microscope (SEM) cross sectionimage to see the internal cross section of a particle for measurement.The particle void volume value is reported as a percentage, calculatedby the volume of the air pockets/volume of the entire particle definedby the external particle boundaries, according to the followingprocedure:

-   -   1) Approximately 100 mg of powder is thoroughly mixed in 5 mL of        epoxy resin.    -   2) The resin is cast in a mold (Electron Microscopy Sciences        part number 70900) and allowed to cure for 1 day.    -   3) After curing, the mold is scored and snapped in half to        present a clean face of cross sectioned particles embedded in        the resin.    -   4) Microscope imaging analysis is performed between 0.1 and 1 KX        at 5 KV. From the cross section, image analysis software (Image        J, National Institute of Health) is used to measure the        cross-sectional diameter of the particle and any cross section        of internal voids.    -   5) The void volume is determined by dividing the sum of void        volumes (calculated from V=4/3*π*r{circumflex over ( )}3) by the        volume of the entire particle and multiplying by 100.

Bulk Density of the particles of the powder is measured by ASTMstandard. The procedure is as follows:

-   -   1) A calibrated Copley BEP2 25 mL density cup is tared on a        scale.    -   2) The cup is filled until overflowing and the excess is scraped        off    -   3) The powder+cup is re-weighed

The weight in grams is divided by 25 mL (volume of cup) and multipliedby 62.428 to convert into pounds/ft{circumflex over ( )}3.

In specific embodiments, the spray-dried powders may have a ParticleSize Distribution in which at least 80%, 85%, 88%, 90%, 91%, 92%, 93%,94%, or 95% of particles in the powder have a particle size of at least80 μm. In various embodiments, the spray-dried powders produced in spraydrying systems of the present disclosure by spray drying processesconducted to provide localized turbulence in the drying fluid,particularly when such localized turbulence is provided throughout theinterior volume of the corresponding spray drying vessel, may have anaverage particle size in a range of from 90 to 120 μm, or in othersuitable range.

The spray-dried powders may in various embodiments have a Particle VoidVolume that is less than 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2.5%, 2%, or1%, of the total particle volume.

In various embodiments, the Bulk Density of the particles of thespray-dried powders may be in a range of from 22 to 40 lb/ft³, or morepreferably in a range of from 25 to 38 lb/ft³.

The present disclosure in various aspects contemplates a spray dryingsystem, comprising:

(a) a spray drying vessel comprising:

-   -   (i) an interior volume arranged to receive an atomized        spray-dryable material and drying fluid for contacting of the        atomized spray-dryable material with the drying fluid in the        interior volume;    -   (ii) at least one drying fluid inlet by which the drying fluid        is introduced into the interior volume for said contacting; and    -   (iii) a spray-dried material outlet communicating with the        interior volume, arranged to discharge spray-dried material and        effluent drying fluid from the vessel;

(b) an atomizer adapted to receive a spray-dryable material anddischarge the atomized spray-dryable material into the interior volumeof the vessel for said contacting;

(c) turbulators positioned to generate localized turbulence in thedrying fluid throughout the interior volume of the vessel; and

(d) a process control unit adapted to regulate flow rate of drying fluidinto the interior volume and flow rate of the spray-dryable material tothe atomizer so that interaction of the drying fluid with theturbulators produces localized turbulence in the drying fluid throughoutthe interior volume of the vessel.

In the above-described spray drying system, the turbulators and processcontrol unit may be adapted to cooperatively provide a turbulencedissipation rate of the localized turbulence in the drying fluid in theinterior volume of the vessel that exceeds 25 m²/sec³. Additionally, oralternatively, the turbulators and process control unit may be adaptedto cooperatively provide the localized turbulence in the drying fluid inthe interior volume of the vessel, wherein the localized turbulence ischaracterized by a Kolmogorov length that is less than an averageparticle size of spray dryable material droplets in the atomizedspray-dryable material.

In such spray drying system, the process control unit may be adapted toregulate temperature of the drying fluid so that the spray drying systemoperates in a low temperature mode of operation.

The turbulators in the above-described spray drying system may comprisenozzles configured to inject pressurized secondary drying fluid into theinterior volume of the vessel, e.g., wherein at least some of thenozzles are provided along a wall of the vessel and/or at a centralregion of the interior volume of the vessel.

The atomizer in the above-described spray drying system may be of anysuitable type and may include one or more selected from among nozzleatomizers, applied charge atomizers, nebulizers, rotary atomizers, andultrasonic atomizers.

The above-describes spray drying system may comprise a drying fluidsource coupled to the after mentioned at least one drying fluid inlet indrying fluid supply relationship with the spray drying vessel. Invarious embodiments, the drying fluid source may be constituted tosupply to the at least one drying fluid inlet of the spray drying vessela drying fluid comprising air, oxygen-enriched air, oxygen, nitrogen,argon, krypton, neon, helium, or a gas mixture comprising two or more ofthe foregoing drying fluid species. In various embodiments, the dryingfluid source may be constituted to supply the drying fluid to the atleast one drying fluid inlet of the spray drying vessel at temperaturebelow at least one of 120° C., 115° C., 110° C., 100° C., 95° C., 90°C., 85° C., 80° C., 75° C., 70° C., 65° C., 60° C., 55° C., 50° C., 45°C., 40° C., 35° C., 30° C., 25° C., and 20° C., and above freezingtemperature of liquid to be volatilized for spray drying of thespray-dryable material, e.g., temperature below 100° C. and abovefreezing temperature of liquid to be volatilized for spray drying of thespray-dryable material.

The above-describes spray drying system may comprise a spray-dryablematerial source arranged in spray-dryable material supply relationshipto the atomizer. Such spray-dryable material source containsspray-dryable material having a viscosity in a range of 500 to 16,000mPa-s and a solvent content that does not exceed 50% by weight, based ontotal weight of the spray-dryable material.

The spray drying system as variously described above may comprise adehumidification assembly arranged to dehumidify the drying fluid sothat it is introduced by the at least one drying fluid inlet into theinterior volume of the vessel for the atomized spray-dryablematerial/drying fluid contacting, at a relative humidity below 35%.

In various embodiments, the above-described spray drying system may beconfigured for electrostatic spray drying. In other embodiments, thespray drying system may comprise a single step spray drying system.

The present disclosure in various aspects contemplates a process forproducing a spray-dried material, comprising:

generating an atomized spray-dryable material;

contacting the atomized spray-dryable material with drying fluid to formspray-dried material;

recovering the spray-dried material from the drying fluid; and

during such contacting, inducing localized turbulence throughout thedrying fluid engaged in the contacting.

Such process may be carried out in which the localized turbulence has aturbulence dissipation rate that exceeds 25 m²/sec³ and/or in which thelocalized turbulence is characterized by a Kolmogorov length that isless than an average particle size of spray dryable material droplets inthe atomized spray-dryable material. The process may be carried out, inwhich the localized turbulence is induced at least in part by injectingpressurized secondary drying fluid into the drying fluid engaged in thecontacting.

In the process as described above, the drying fluid may comprise air,oxygen-enriched air, oxygen, nitrogen, argon, krypton, neon, helium, ora gas mixture comprising two or more of the foregoing drying fluidspecies.

The drying fluid in the above-described process may be introduced to thecontacting at temperature below at least one of 120° C., 115° C., 110°C., 100° C., 95° C., 90° C., 85° C., 80° C., 75° C., 70° C., 65° C., 60°C., 55° C., 50° C., 45° C., 40° C., 35° C., 30° C., 25° C., and 20° C.,and above freezing temperature of liquid to be volatilized to form thespray-dried material. In specific embodiments, the drying fluid may beintroduced to the contacting at temperature below 100° C., and abovefreezing temperature of liquid to be volatilized to form the spray-driedmaterial.

The above-described process may be carried out, wherein average particlesize of spray-dryable material droplets in the atomized spray-dryablematerial in the contacting is in a range of from 50 to 300 μm. Thedrying fluid in the above-described process may be introduced to thecontacting at relative humidity below 35%. The spray-dryable material inthe above-described process may have a viscosity in a range of 500 to16,000 mPa-s and a solvent content that does not exceed 50% by weight,based on total weight of the spray-dryable material. The above-describedprocess may be conducted, in which an electrostatic charge is applied tothe atomized spray-dryable material or to spray-dryable material fromwhich the atomized spray-dryable material is generated, e.g., with anapplied voltage in a range of from 0.5 to 75 kV.

Referring now to the drawings, FIG. 1 is a schematic representation of aspray drying process system 10 according to one embodiment of thepresent disclosure.

As shown, the spray drying process system 10 comprises a spray dryer 12including a spray drying vessel 14 having an upper cylindrical portion18 and a downwardly convergent conical shaped lower portion 16. Thespray drying vessel 14 in this embodiment is equipped with an array ofpuffer jets 20 installed in two circumferentially extending,longitudinally spaced apart rows in which each puffer jet iscircumferentially spaced from the adjacent puffer jets in the row. Eachof the puffer jets in the respective rows is arranged to be suppliedwith secondary drying fluid by the secondary fluid feed lines 24associated with the source structure 22, which may extendcircumferentially around the spray drying vessel 14, so that each of thepuffer jets is connected with a secondary fluid feed line 24 in the samemanner as the puffer jets shown at opposite sides of the spray dryingvessel 14 in the system as depicted in FIG. 1.

The secondary fluid source structure 22 is depicted schematically, butmay be constituted by suitable piping, valving, and manifoldingassociated with a secondary fluid supply tank and pumps, compressors, orother motive food drivers producing a flow of pressurized secondarydrying fluid introduced to the puffer jets 20 in the secondary fluidfeed lines 24.

At the upper end of the spray drying vessel 14, an inlet 26 is provided,to which the spray dryable liquid composition to be spray dried in thespray drying vessel 14 is flowed in liquid composition feed line 40under the action of liquid composition pump 38 receiving the liquidcomposition in liquid composition supply line 36 from the liquidcomposition supply vessel 28. The liquid composition to be spray driedmay be formulated in the liquid composition supply vessel 28, to whichingredient of the liquid composition may be supplied for mixing therein,e.g., under the action of a mixer device internally disposed in theliquid composition supply vessel 28 (not shown in FIG. 1). Such mixerdevice may be or include a mechanical mixer, static mixer, ultrasonicmixer, or other device effecting blending and homogenization of theliquid composition to be subsequently spray dried.

For example, when the liquid composition of the spray dried is a slurryor emulsion of solvent, carrier, and product material, the solvent maybe supplied to the liquid composition supply vessel 28 from a solventsupply vessel 30, carrier material may be provided to the liquidcomposition supply vessel 28 from a carrier material supply vessel 32,and product material may be provided to the liquid composition supplyvessel 28 from a product material supply vessel 34, as shown.

The liquid composition to be spray dried thus is flowed from the liquidcomposition supply vessel 28 through liquid composition supply line 36to pump 38, and then flows under action of such pump in liquidcomposition feed line 40 to the inlet 26 of the spray drying vessel 14to a spray device such as an atomizer or nozzle disposed in the inletregion of the interior volume of the spray drying vessel. Concurrently,main drying fluid is flowed in main drying fluid feed line 70 to theinlet 26 of the spray drying vessel 14, for flow through the interiorvolume of the spray drying vessel from the upper cylindrical portion 18thereof to the lower conical portion 16 thereof, at the lower end ofwhich the dried powder product and effluent drying fluid flow into theeffluent line 42. During flow of the main drying fluid through theinterior volume of the spray drying vessel 14, the puffer jets 20 areselectively actuated to introduce secondary drying fluid at suitablepressure and flow rate to induce localized turbulence in the interiorvolume, in the drying fluid flow stream, for enhancement of masstransfer and drying efficiency of the spray drying vessel.

The dried powder product and effluent drying fluid flowing in theeffluent line 42 pass to the cyclone separator 44, in which the driedpowder solids are separated from the effluent drying fluid, with theseparated solids passing in product feed line 46 to the dried powderproduct collection vessel 48. The dried powder product in the collectionvessel 48 may be packaged in such vessel, or may be transported to apackaging facility (not shown in FIG. 1) in which the collected driedpowder product is packaged in bags, bins, or other containers forshipment and ultimate use.

The effluent drying fluid separated from the dried powder product in thecyclone separator 44 flows in effluent fluid feed line 52 the baghouse52 in which any residual entrained fines in the effluent fluid areremoved, to produce a fines-depleted effluent fluid that then is flowedin effluent fluid transfer line 54 to blower 56, from which the effluentfluid is flowed in blower discharge line 58 to the condenser 60 in whichthe effluent fluid is thermally conditioned as necessary, with thethermally conditioned effluent fluid than being flowed in recycle line62 to blower 64, from which the recycled effluent fluid flows in pumpdischarge line 66 to dehumidifier 68 in which residual solvent vapor isremoved to adjust the relative humidity and dewpoint characteristics ofthe drying fluid to appropriate levels for the spray drying operation,with the dehumidified drying fluid then flowing in main drying fluidfeed line 70 to the inlet 26 of the spray drying vessel 14, aspreviously described. The dehumidifier may in various embodiments beconstructed and arranged to provide both the primary drying fluid andthe secondary drying fluid to the spray drying vessel 14 at apredetermined relative humidity and dewpoint characteristic, or multipledehumidifiers may be provided in the spray drying system for suchpurpose.

FIG. 2 is a schematic representation, in breakaway view, of a portion ofthe spray drying process system of FIG. 1, showing the action oflocalized turbulence induction in the spray drying vessel of the system.

As depicted, the inlet 26 of the spray dryer 14 includes a top wall 80on which the inlet 26 is reposed, receiving main drying fluid in maindrying fluid feed line 70, and spray dryable liquid composition inliquid composition feed line 40. In the inlet, the introduced spraydryable liquid composition flows into the atomizer nozzle 88 extendingthrough the top wall 80, and is discharged at the open lower end of suchnozzle as an atomized spray 76 of liquid droplets 84 that fall throughthe interior volume of the spray drying vessel 14, in the directionindicated by arrow A, while being contacted with the main drying fluidintroduced from main drying fluid feed line 70 to the inlet 26, for flowthrough openings 82 in the top wall 80, with the main drying fluid thenflowing downwardly as indicated by arrows 78, so that the co-currentlyintroduced main drying fluid and atomized liquid droplets 84 arecontacted with one another.

During such contacting of the main drying fluid and droplets of theatomized spray dryable liquid composition, the puffer jet 20 is actuatedby an actuation signal transmitted in signal transmission line 202 fromCPU 200, to initiate injection of secondary drying fluid supplied in thein the secondary fluid feed line 24 from the distal nozzle 72 of thepuffer jet, to introduce a turbulent injected flow 74 of secondarydrying fluid that in interaction with the main drying fluid flow streamcreates a localized turbulence region 86 in the interior volume of thespray drying vessel 14, to enhance mass transfer and drying efficiency.

The CPU 200 thus may be programmably arranged and constructed to actuatethe puffer jet 20 intermittently, cyclically and repetitively, toprovide a series of bursts of turbulent secondary drying fluid into themain drying fluid flow stream that disruptively and intensively mixesthe drying fluid with the droplets of atomized liquid composition, andwherein others of the multiple puffer jets associated with the spraydrying vessel 14 may be synchronously or asynchronously actuated inrelation to puffer jet 20, in any suitable pattern and timing scheduleof “firings” of individual puffer jets in the overall system.

FIG. 3 is a graphical depiction of particle trajectories in a tangentialinlet rotary atomizer spray dryer, as calculated using computationalfluid dynamics, illustrating the movement of the particles to the outerwall of the dryer, leaving a substantial volume that is devoid ofparticles, in the absence of puffer jet instigation of localizedturbulence in accordance with the present disclosure.

The spray dryer vessel utilized in this depiction has a cylindricalgeometry with a tangential air inlet, in which particles of the spraydryable liquid composition are atomized by a rotating atomizer locatedin the center top portion of the spray dryer vessel. Particles releasedfrom the atomizer initially travel radially outward until slowed by airdrag, becoming entrained in the flow field of the spray dryer vessel.The particles are pushed by this flow through the interior volume of thespray dryer vessel and out the bottom discharge port of the spray dryervessel.

In this type of geometry, the center region of the interior volume ofthe spray dryer vessel has a low density of particles due to the actionof the air flow and the centripetal acceleration on the particles. Theair (drying fluid) in this region also has a much lower water vaporconcentration than the flow with the entrained particles. Most of thiscentral region of significantly drier air does not become mixed with theouter region of flow where the particles are entrained until leaving thespray dryer vessel, whereupon it finally becomes mixed with the particleladen air. Nonetheless, because the contact time from the outlet of thespray dryer vessel to the cyclone unit is short, on the order of a fewseconds, the mixing effect is insignificant and the air leaves withoutbeing fully utilized. Similar effects can also be observed in verticalairflow spray dryer vessel geometries, in which the particledistribution throughout the dryer volume is also very non-homogeneous.

By utilizing an array of puffer jets in accordance with the presentdisclosure, the above-described inhomogeneity in the interior volume ofthe spray dryer vessel can be minimized or even eliminated, to achieveorder of magnitude increases in diffusivity in regions that in theabsence of localized turbulence generation would be grosslyunderutilized in terms of the drying capacity of the drying fluid insuch regions.

FIG. 4 is a graphical depiction of a computational fluid dynamicssimulation of effect on total diffusivity caused by turbulent puffsintroduced into airflow in a rectangular duct, 1.5 seconds after thepuff has occurred. The plot shows the evolution of the total diffusivityalong a vertical center plane of the duct one and a half seconds afteroccurrence of the puffs. The puffs were introduced at time=1 second. Airenters from the left end of the duct and exits from the right end.Turbulent puffs are introduced by two nozzles located on the top of theduct along the longitudinal centerline. The puffs are directedperpendicular to the main flow. This diffusivity profile persists for upto 5 seconds, propagating along the duct.

FIG. 4 thus illustrates through the use of computational fluid dynamicsthe effect of turbulence on the diffusivity for two jets, each injectinga high velocity jet of air into a linear rectangular duct with airflowing through it at a linear velocity of 1 meter/second. The jets turnon at one second from the time the duct flow is established. The puffshave a duration of one second, introducing a high speed flow at rightangles to the main flow traveling in the duct, producing a region ofturbulence in the flow. In the turbulent region the diffusivity hasincreased by over 50% as shown in FIG. 4. At the initial introduction ofthe puff, the diffusivity increased by an order of magnitude. Thiseffect will also increase the drying rate by nearly an order ofmagnitude in the affected regions, dramatically improving theutilization of the dry process air and improving the overall energyefficiency of the process. The turbulent effects persist for an extendedperiod of time, on the order of many seconds, much longer than theduration of the pressure pulse that produced the puff. The spatialextent of the puff increases linearly with distance traveled asillustrated in FIG. 4. The puff volume also scales as the cube of thepuff width, thus enabling the effects to increasingly effect the entireflow volume in the spray drying chamber.

Thus, by placing a series of air injection nozzles around thecircumference of a spray dryer vessel and periodically pulsing thenozzles on, the powder particles in these turbulent regions willexperience higher concentration gradients and higher drying rates. Theextended spatial region of the turbulent mixing created by the puffswill enable more complete and continued mixing of the air and particlesthroughout the volume of the spray drying chamber. A further advantageof the turbulent puffers, as discussed, is accelerated cooling of theparticles by injecting air at room temperature before leaving the dryer,of particular importance when the material being dried has a low classtransition temperature. This method of introduction of purposefulturbulent mixing has not to our knowledge been previously used in spraydrying processes and represents a novel utilization of turbulent effectsfor significantly increasing the efficiency of the spray drying processin a manner not previously appreciated in the spray drying industry.

FIG. 5 is a schematic representation of a spray drying apparatusaccording to one embodiment of the present disclosure, featuring anarray of turbulent mixing nozzles on the spray drying chamber wall,configured for injection of transient, intermittent turbulent air burstsinto the main drying fluid flow stream in the spray drying chamber.

As illustrated in FIG. 5, the spray drying apparatus 300 includes acylindrical wall 302 that at its upper extremity is secured to acircular top wall 304 having a central opening therein to accommodate aspray atomizer (not shown in FIG. 5) for spraying an atomized emulsioninto the interior volume of the spray drying chamber bounded by suchcylindrical and top walls. The spray drying apparatus further includes afrustoconical lower wall 308 that at its lower end is joined to acylindrical conduit 312, which may be provided with an air seal or otherclosure element that is selectively openable to remove dried materialfrom the apparatus.

The spray drying apparatus thereby encloses an interior volume toprovide a spray drying chamber in which the sprayed emulsion atomizedparticles are contacted with drying air, introduced to the chamberthrough the air inlet passage 306 at the upper portion of the spraydryer. The spray dryer at an upper portion of the frustoconical wall 308is provided with a takeoff conduit 310 through which the dryingair/particles mixture may be discharged from the spray drying chamberand conveyed to a cyclone for fluid/solid separation.

The cylindrical wall 302 is provided with axially spaced-apart rows 316,318, and 320 of turbulent air injection nozzles 322. In each of therows, the nozzles are circumferentially spaced apart around the fullcircumference of the wall. In this arrangement, the nozzles are arrangedin a circular pattern with intervening spacing such that the spatialenvelope of each nozzle overlaps to some extent the spatial envelope ofthe next adjoining nozzle in the array. The nozzles in the second row318 are offset by an appropriate angle, in relation to the nozzles inthe and first and third rows, to improve the volumetric coverage of theinjected turbulent fluid.

The nozzles are depicted as tubular elements in the schematicrepresentation of FIG. 5, for ease of reference, but it will beappreciated that each of the nozzles is coupled in gas flowcommunication with a source of pressurized air. Such coupling may beeffected by a manifold conduit circumscribing the cylindrical wall 302which is connected to the outer (proximal) end of the nozzle, so thatthe nozzles constitute branches of the manifolded flow circuitry. Theindividual nozzles may be provided with flow control valves equippedwith pneumatic or other type actuators, so that high-pressure air may bemaintained in the manifold conduit, and injected, upon opening of thevalve in the individual nozzle, into the interior volume of the spraydrying chamber. In such arrangement, the actuators of the respectiveflow control valves may be coupled to a cycle timer apparatus, e.g., acentral processor unit (CPU), microprocessor, programmable logic unit,or other device for cyclically and repetitively opening the valves inthe respective nozzles to effect a burst of injected air from thenozzles at their proximal ends, with the control device serving to causethe valve actuators to close the valves at the end of the desiredduration of the air injection operation. The nozzle may have a singleorifice or comprise an array of orifices, with the orifice size selectedto ensure adequate penetration of the bursts of injected air into theinterior volume of the spray dryer.

In an illustrative embodiment, each of the nozzles may have a fluiddispensing “on” duration in a range of from 0.1 to 100 seconds. In otherembodiments, the duration of such “on” time may be in a range of from0.1 to 60 seconds. The excitation pressure applied to the nozzle in the“on” state may be any suitable value, and may for example be a pressurein a range of from 1 to 200 psi, with a volumetric flow rate of from 1to 100 ft.³ per minute, as appropriate for the spray dryer specific sizeand so as not to disrupt the spray dryer main airflow pattern. The dutycycle of the nozzles can range from 1% to 100%, depending on the dryerairflow. The nozzles can be individually excited or turned on inspecially configured arrangements or all excited simultaneously asrequired for a specific dryer operation. For example, the spray dryerillustratively shown in FIG. 5 may be operated with all nozzles turnedon simultaneously, and subsequently simultaneously turned off after an“on” duration of 1 second. The nozzles then remain “off” for a period of5 seconds, following which the cycle is repeated. The delay between the“off” state and the following “on” state is determined primarily by thetime it takes for damping of the localized induced turbulence to occur.

The specific timing and duration of the respective “on” and “off”portions of the cyclic air injection process during spray drying ofemulsified material in the spray dryer may be determined empirically bythose of ordinary skill in the art, based on the disclosure herein,e.g., by hydrodynamic modeling and/or deployment of nozzles in aselected pattern on the spray drying chamber and determination of therelevant characteristics of the spray dried material discharged from thechamber for different specific cycles of air injection.

Accordingly, the present disclosure represents a major advance in theart of spray drying of spray dryable liquid compositions to form spraydried product, in an ultrahigh efficiency manner.

The present disclosure may therefore be implemented, utilizing a methodof processing a spray dryable liquid composition to form a spray driedproduct, such method comprising: generating a spray of the spray dryableliquid composition; contacting the spray of spray dryable liquidcomposition in a spray drying contact zone with a stream of primarydrying fluid; injecting pressurized secondary drying fluid into thestream of primary drying fluid in the spray drying contact zone atmultiple loci thereof to provide localized turbulence at said multipleloci; and recovering the spray dried product from the spray dryingcontact zone. This method may be further implemented with any one ormore of the following features (A)-(S), to the extent that any suchmultiple features are compatible with one another:

(A) the primary drying fluid and secondary drying fluid are introducedto the spray drying contact zone at temperature below 100° C. and abovefreezing temperature of solvent in the spray dryable liquid composition;

(B) the injecting is continuously conducted during the contacting;

(C) the injecting is intermittently conducted during the contacting;

(D) the injecting is carried out according to a predetermined injectingschedule, in a cyclic repeating manner;

(E) the primary drying fluid and secondary drying fluid are eachindependently selected from the group consisting of air, oxygen,oxygen-enriched air, nitrogen, helium, argon, neon, carbon dioxide,carbon monoxide, and combinations of two or more of the foregoing;

(F) the primary drying fluid and secondary drying fluid are each air;

(G) the spray dryable liquid composition comprises at least one productmaterial selected from the group consisting of food materials, beveragematerials, fragrance materials, pigment materials, flavor materials,pharmaceutical materials, therapeutic materials, medication materials,homeopathic materials, biological materials, probiotic materials,construction materials, formulating materials, and mixtures, blends,composites, and combinations of two or more different materials of theforegoing;

(H) the spray dryable liquid composition comprises at least oneingredient selected from the group consisting of solvents, carriers,adjuvants, excipients, surfactants, anti-agglomerants, anti-cakingagents, co-active ingredients, wetting agents, dispersants, emulsifiers,stabilizers, antioxidants, preservatives, encapsulants, pore-formingagents, hardeners, and mixtures, blends, composites, and combinations oftwo or more ingredients of the foregoing;

(I) the spray dryable liquid composition comprises an aqueouscomposition;

(J) the spray dryable liquid composition comprises solvent selected fromthe group consisting of water, alcohol, and aqueous alcohol solution;

(K) the spray dryable liquid composition comprises at least one carrier,e.g., selected from the group consisting of carbohydrates, proteins,lipids, waxes, cellulosic materials, sugars, starches, and natural andsynthetic polymeric materials;

(L) the spray dryable liquid composition has a viscosity in a range offrom 300 mPa-s to 28,000 mPa-s, e.g., from 500 mPa-s to 16,000 mPa-s, ormore specifically from 1000 mPa-s to 4000 mPa-s;

(M) the spray dryable liquid composition comprises from 20 to 50% byweight of solvent, based on total weight of the spray dryable liquidcomposition;

(N) the solvent comprises water;

(O) the primary drying fluid and secondary drying fluid are introducedto the spray drying contact zone at temperature below at least one of95° C., 90° C., 85° C., 80° C., 75° C., 70° C., 65° C., 60° C., 55° C.,50° C., 45° C., 40° C., 35° C., 30° C., 25° C., and 20° C., and whereinsuch temperature is above freezing temperature of solvent in the spraydryable liquid composition;

(P) the primary drying fluid and secondary drying fluid are introducedto the spray drying contact zone at below 20% relative humidity;

(Q) the primary drying fluid and secondary drying fluid are introducedto the spray drying contact zone at relative humidity below at least oneof 18%, 15%, 12%, 10%, 8%, 5%, 2.5%, 2%, 1.5%, 1% and 0.5% relativehumidity;

(R) the spray of spray dryable liquid composition comprises droplets ofsize in a range of from 10 to 300 μm; and

(S) the injecting is controlled with a control system executing apredetermined cycle timer program.

In various embodiments, a spray drying system in accordance with thepresent disclosure may be utilized, as comprising: a spray drying vesselincluding an interior volume for contacting of introduced spray dryableliquid composition and a stream of primary drying fluid, said vesselincluding a spraying device positioned to introduce a spray of the spraydryable liquid composition into the interior volume for said contacting,an inlet for introduction of the primary drying fluid to the interiorvolume, and an outlet for discharging spray dried product and effluentdrying fluid from the interior volume; and a multiplicity of secondaryfluid injectors constructed and arranged to introduce pressurizedsecondary drying fluid into the interior volume at flow conditionsproviding localized turbulence in the stream of primary drying fluid inthe interior volume at multiple loci in the stream of primary dryingfluid. Such spray drying system may be deployed, in variousarrangements, comprising any one or more of the following features(A)-(X), to the extent that any such multiple features are compatiblewith one another:

(A) the multiplicity of secondary fluid injectors are mounted on thespray drying vessel in an array;

(B) the spray drying vessel comprises a cylindrical portion on which thearray of secondary fluid injectors is mounted;

(C) the array of secondary fluid injectors comprises at least onecircumferentially extending row of secondary fluid injectors, eachsecondary fluid injectors in each such row being circumferentiallyspaced apart from adjacent secondary fluid injectors in such row, andwherein multiple rows when present are axially spaced apart with respectto a central axis of the spray drying vessel;

(D) each of the multiplicity of secondary fluid injectors is actuatedfor secondary fluid injection by a control system;

(E) the control system is constructed and arranged to execute a cycletimer program for actuation of the secondary fluid injectors;

(F) each of the multiplicity of secondary fluid injectors is actuatableto supply a transient burst of secondary fluid to the interior volume ofthe spray drying vessel;

(G) a selected one or ones of said multiplicity of secondary fluidinjectors is actuatable by the control system to supply a transientburst of secondary fluid to the interior volume of the spray dryingvessel, while selected others of said multiplicity of secondary fluidinjectors are deactuated, in a predetermined sequence in which each ofthe multiplicity of secondary fluid injectors is intermittently actuatedin the predetermined sequence;

(H) each of the multiplicity of secondary fluid injectors is actuatableto continuously supply secondary fluid to the interior volume of thespray drying vessel during spray drying operation therein;

(I) flow circuitry receiving spray dried product and effluent dryingfluid from the outlet of the spray drying vessel, said flow circuitrycontaining a fluid/solids separator constructed and arranged to separatespray dried product from the effluent drying fluid, and a dehumidifierconfigured to dry the effluent drying fluid, from which spray driedproduct has been separated, to a predetermined extent, said flowcircuitry being constructed and arranged to recycle the drying fluid,subsequent to its being dried by the dehumidifier, to the inlet of thespray drying vessel, as at least part of the primary drying fluidintroduced to the interior volume of the spray drying vessel;

(J) a primary drying fluid source constructed and arranged to provideprimary drying fluid to the spray drying vessel at temperature below100° C. and above freezing temperature of solvent in the spray dryableliquid composition;

(K) a control system constructed and arranged for operation of themultiplicity of secondary fluid injectors;

(L) a source of primary drying fluid and a source of secondary dryingfluid;

(M) each of the respective sources of primary drying fluid and secondarydrying fluid independently contains a fluid selected from the groupconsisting of air, oxygen, oxygen-enriched air, nitrogen, helium, argon,neon, carbon dioxide, carbon monoxide, and combinations of two or moreof the foregoing;

(N) a source of the spray dryable liquid composition;

(O) the source of the spray dryable liquid composition contains spraydryable liquid composition comprising at least one product materialselected from the group consisting of food materials, beveragematerials, fragrance materials, pigment materials, flavor materials,pharmaceutical materials, therapeutic materials, medication materials,homeopathic materials, biological materials, probiotic materials,construction materials, formulating materials, and mixtures, blends,composites, and combinations of two or more different materials of theforegoing;

(P) the source of the spray dryable liquid composition contains spraydryable liquid composition comprising at least one ingredient selectedfrom the group consisting of solvents, carriers, adjuvants, excipients,surfactants, anti-agglomerants, anti-caking agents, co-activeingredients, wetting agents, dispersants, emulsifiers, stabilizers,antioxidants, preservatives, encapsulants, pore-forming agents,hardeners, and mixtures, blends, composites, and combinations of two ormore ingredients of the foregoing;

(Q) the source of the spray dryable liquid composition contains anaqueous spray dryable liquid composition;

(R) the source of the spray dryable liquid composition contains spraydryable liquid composition comprising at least one carrier selected fromthe group consisting of carbohydrates, proteins, lipids, waxes,cellulosic materials, sugars, starches, and natural and syntheticpolymeric materials;

(S) the source of the spray dryable liquid composition contains spraydryable liquid composition having a viscosity in a range of from 300mPa-s to 28,000 mPa-s;

(T) the source of the spray dryable liquid composition contains spraydryable liquid composition having a viscosity in a range of from 500mPa-s to 16,000 mPa-s;

(U) the source of the spray dryable liquid composition contains spraydryable liquid composition having a viscosity in a range of from 1000mPa-s to 4000 mPa-s;

(V) the source of the spray dryable liquid composition contains spraydryable liquid composition comprising from 20 to 50% by weight ofsolvent, based on total weight of the spray dryable liquid composition;

(W) a primary drying fluid source constructed and arranged to provideprimary drying fluid to the spray drying vessel at temperature below atleast one of 95° C., 90° C., 85° C., 80° C., 75° C., 70° C., 65° C., 60°C., 55° C., 50° C., 45° C., 40° C., 35° C., 30° C., 25° C., and 20° C.,and wherein such primary drying fluid temperature is above freezingtemperature of solvent in the spray dryable liquid composition, andcomprising a secondary drying fluid source constructed and arranged toprovide secondary drying fluid to the spray drying vessel at temperaturebelow at least one of 95° C., 90° C., 85° C., 80° C., 75° C., 70° C.,65° C., 60° C., 55° C., 50° C., 45° C., 40° C., 35° C., 30° C., 25° C.,and 20° C., and wherein such secondary drying fluid temperature is abovefreezing temperature of solvent in the spray dryable liquid composition;

(X) a dehumidifier constructed and arranged to provide the primarydrying fluid and secondary drying fluid to the interior volume of thespray drying vessel at below 20% relative humidity, e.g., a dehumidifierconstructed and arranged to provide the primary drying fluid andsecondary drying fluid to the interior volume of the spray drying vesselat relative humidity below at least one of 18%, 15%, 12%, 10%, 8%, 5%,2.5%, 2%, 1.5%, 1% and 0.5% relative humidity.

In various embodiments, a spray drying apparatus may be utilized,comprising: a spray drying chamber having an interior volume andconfigured for introduction of spray dryable material into the interiorvolume for drying therein, and discharge of dried material and dryingfluid therefrom; a primary drying fluid inlet configured for introducingprimary drying fluid into the interior volume of the chamber for contactwith the spray dryable material in the interior volume, to provide aprimary drying fluid flow stream through the interior volume; and amultiplicity of secondary drying fluid inlets configured forintermittent injection of secondary drying fluid into the primary dryingfluid flow stream to effect transient localized turbulence in theprimary drying fluid flow stream, or alternatively for continuousinjection of secondary drying fluid into the primary drying fluid flowstream, for enhancement of drying of the spray dryable material in theinterior volume of the chamber.

The primary drying fluid inlet may be constituted by a single fluidinlet, or it may be constituted by a multiplicity of primary dryingfluid inlets joined to a single or multiple sources of primary dryingfluid, and the design of such primary drying fluid inlets may be such asto impart a high degree of localized turbulence in the introduced dryingfluid in the region of primary drying fluid introduction in the interiorvolume of the spray drying vessel.

In such spray drying apparatus, the multiplicity of secondary dryingfluid inlets may comprise secondary drying fluid inlets arranged in acircumferentially spaced apart arrangement around a circumscribing wallof the spray drying chamber. In various embodiments, the multiplicity ofsecondary drying fluid inlets may comprise multiple vertically spacedapart rows of secondary drying inlets on the circumscribing wall of thespray drying chamber. The secondary drying fluid inlets in suchembodiments may in successively vertically spaced apart rows becircumferentially offset in relation to one another.

The secondary drying fluid inlets may also include inlets disposed in acentral region of the interior volume of the spray drying vessel forintroduction of secondary drying fluid in such manner as to providelocalized turbulence in the flowstream of drying fluid in the centralregion of the interior volume of the spray drying vessel. In variousembodiments, the central region secondary drying fluid inlets maycomprise jets or injectors supplied with secondary drying fluid thatproduce localized turbulence in the central region of the interiorvolume of the spray drying vessel, e.g., jets or injectors on a centralvertically upstanding secondary drying fluid feed conduit arranged tosupply the jets or injectors with secondary drying fluid.

The spray drying apparatus as variously described above may comprise asecondary drying fluid assembly coupled with the secondary drying inletsand configured to introduce secondary drying fluid in accordance with apredetermined cycle time program.

The primary drying fluid and secondary drying fluid may be the same asor different from one another, and may comprise air or any othersuitable fluid for the specific spray drying operation and apparatusinvolved.

The spray drying apparatus as variously described above may furthercomprise a source of spray dryable material arranged in communicationwith the spray drying chamber interior volume for spray delivery of thespray dryable material to the interior volume of the spray dryingchamber.

In various embodiments, the above-described spray drying apparatus mayfurther comprise a dehumidifier configured to provide dehumidified airto the primary drying fluid inlet and to the secondary drying fluidinlets.

The spray drying apparatus may be further constructed and arranged invarious embodiments so that intermittent injection of secondary dryingfluid into the primary drying fluid flow stream to effect transientlocalized turbulence in the primary drying fluid flow stream iscontrolled by an injection controller configured to inject secondarydrying fluid through the secondary drying fluid inlets for an injectionperiod in a range of from 0.1 to 100 seconds.

It will be further recognize that the number, pattern, and orientationof the nozzles or other injection devices may be widely varied in thebroad practice of the present disclosure. In various embodiments, thenozzles or injection devices may be oriented to inject fluid generallytransversely to a main direction of flow of the primary drying fluidflow stream, but it may also be advantageous in other embodiments todirect the secondary drying fluid into the primary drying fluid flowstream at any suitable angle, orthogonal, oblique, acute, etc. withreference to the main direction of flow of the primary drying fluid flowstream, and in still other embodiments, combinations of differentorientations of the nozzles or injection devices may be utilized toachieve the desired drying efficiency and character.

In accordance with the present disclosure, a method of spray drying aspray dryable material may be carried out, comprising processing of thespray dryable material in a spray drying apparatus according to any ofthe embodiments described herein.

In such method, the pressure of the secondary drying fluidintermittently injected into the primary drying fluid flow stream may bein a range of from 1 to 200 psig. The method may be conducted so thatthe secondary drying fluid is intermittently injected for an injectionperiod in a range of from 1 to 5 seconds, and so that successiveinjection periods are separated by a non-injection period in a range offrom 1 to 5 seconds.

In accordance with the present disclosure, a method of spray drying of aspray dryable material in a primary drying fluid flow stream may becarried out, comprising intermittently, transiently, and cyclicallyinjecting secondary drying fluid into the primary drying fluid flowstream at multiple loci in the primary drying fluid flow stream, so asto create transient localized turbulence at such loci that enhancesdrying of the spray dryable material, or alternatively, continuouslyinjecting secondary drying fluid into the primary drying fluid flowstream at multiple loci in the primary drying fluid flow stream, so asto create localized turbulence at such loci that enhances drying of thespray dryable material.

Such spray drying method may be carried out as variously describedherein, with respect to specific cycle times, pressures, andconfigurations and arrays of nozzles or other injector devices forproviding transient localized turbulence in the primary drying fluidstream in which the sprayed material is to be dried, or foralternatively providing continuous localized turbulence in the primarydrying fluid stream in which the sprayed material is to be dried.

In the above-described methods and apparatus of the present disclosure,the primary drying fluid flow stream and the secondary drying fluid maycomprise a same fluid, or alternatively may comprise different fluids.In various embodiments, the primary drying fluid and the secondarydrying fluid are air. The spray dryable material in such methods andapparatus may be of any suitable type, as previously described, and mayfor example comprise a flavor, fragrance, food, beverage, comestible, orpharmaceutical material or ingredient.

In the above-described methods and apparatus of the disclosure, themultiple loci in the primary drying fluid flow stream may comprise lociat a peripheral region of the fluid flow stream. The direction ofinjection of the secondary drying fluid into the primary drying fluidflow stream, as indicated, may be transverse to a direction of flow ofthe primary drying fluid flow stream. In various embodiments, themultiple loci in the primary drying fluid flow stream may comprise locithat are spaced along a direction of flow of the primary drying fluidflow stream. In other embodiments, the multiple loci may comprise locithat are generally in a same transversely oriented plane in reference tothe direction of flow of the primary drying fluid flow stream, as wellas loci that are spaced along a direction of flow of the primary dryingfluid flow stream. It will be appreciated that the specific patterns ofsecondary drying fluid injection may be widely varied within the broadpractice of the present disclosure.

Thus, although the disclosure specifically contemplates pulsedintermittent injections of fluid into the main drying fluid flow streamin the spray drying chamber, as a preferred mode of operation,embodiments also are contemplated in which the injections of fluid intothe main drying fluid flow stream are carried out continuously.

In accordance with the disclosure, a spray drying apparatus may beutilized, comprising: a spray drying chamber having an interior volumeand configured for introduction of spray dryable material into theinterior volume for drying therein, and discharge of dried material anddrying fluid therefrom; a primary drying fluid inlet configured forintroducing primary drying fluid into the interior volume of the chamberfor contact with the spray dryable material in the interior volume, toprovide a primary drying fluid flow stream through the interior volume;and a multiplicity of secondary drying fluid inlets configured forinjection of secondary drying fluid into the primary drying fluid flowstream to effect localized turbulence in the primary drying fluid flowstream, for enhancement of drying of the spray dryable material in theinterior volume of the chamber, or alternatively for continuousinjection of secondary drying fluid into the primary drying fluid flowstream.

In various embodiments, a method of spray drying of a spray dryablematerial may be performed, comprising use of the apparatus described inthe preceding paragraph.

In accordance with the disclosure, a method of spray drying of a spraydryable material in a primary drying fluid flow stream may be conducted,comprising injecting secondary drying fluid into the primary dryingfluid flow stream at multiple loci in the primary drying fluid flowstream, so as to create localized turbulence at such loci that enhancesdrying of the spray dryable material.

The process, apparatus, and systems of the present disclosure mayutilize any suitable duty cycle, e.g., a duty cycle within a range offrom 1%400%. In various embodiments, the duty cycle may be in a range offrom 1% to 99%, from 1% to 95%, from 5% to 90%, from 10% to 80%, from15% to 75%, from 25% to 70%, or any other duty cycle range bounded byany one of the aforementioned minimum values and any other mentionedupper values, as appropriate to a specific implementation of the presentdisclosure.

The process, apparatus, and systems of the present disclosure enable asubstantial improvement in the utilization of the drying capacity of thedry air that is supplied to the spray dryer, as compared to utilizationlevels that are typical of prior conventional spray drying systems. Byproviding purposefully generated localized turbulent mixing in the spraydryer, a high level of utilization of the drying capacity of the dry air(or other drying fluid) supplied to the spray drying vessel is achieved.This in turn enables the overall efficiency of the spray dryingoperation to be substantially increased.

In preferred practice, the apparatus, process, and systems of thepresent disclosure for injected turbulent fluid creation of localizedturbulence in the flow stream of drying fluid in a spray drying vesselor a spray drying zone are utilized in low temperature spray dryingoperations, wherein the temperature of the drying fluid (including bothprimary (main) drying fluid and secondary drying fluid) is below 100° C.and above the freezing point of the solvent in the material being spraydried.

FIG. 6 is a scanning electron microscope (SEM) image, at magnificationof 0.51 k×, of a cross section of a particle produced by low temperaturespray drying, as representative of dry powder product produced inaccordance with the methods and apparatus of the present disclosure. Asis apparent from the image, the spray dried powder product is highlyhomogeneous in morphology and appearance, with the active ingredient ofthe product, visible as black dots, being uniformly dispersed in the(starch) carrier material.

FIG. 7 is a depiction of drying fluid stream lines in a spray dryingvessel in which a main flow of drying fluid is introduced at an upperportion of the vessel, with additional drying fluid being introduced formaintenance of a fluidized bed in a lower portion of the spray dryingvessel, and with spray drying fluid being discharged from dischargeports at an upper and outer portion of the spray drying vessel. Suchspray drying vessel is of a type more fully described in connection withFIG. 9, but wherein the fluid injector jet augmentation of the spraydrying vessel shown in FIG. 9 is not present.

FIG. 8 is a depiction of particle trajectories in a spray drying vesselof the type for which drying fluid stream lines are depicted in FIG. 7.As is evident in the FIG. 8 depiction, this spray dryer design has largevolumes in which the number density of particles is low. These lownumber density volumes are a source of loss of drying efficiency.Particle residence times in this type of spray dryer may be on the orderof 10-15 seconds, which necessitates a fluidized bed arrangement in alower portion of the spray drying vessel, in order to achieve spraydrying of the spray dryable feed material to a dry powder product.

FIG. 9 is a schematic representation of a spray drying system accordingto another embodiment of the present disclosure, comprising a spraydrying vessel of the general type for which air stream lines andparticle trajectories are shown in FIGS. 7 and 8, respectively, butwherein an array of fluid injector jets is provided, mounted on thespray drying vessel wall and arranged to inject fluid into the interiorvolume of the vessel, to enhance spray drying efficiency of the system.

The FIG. 9 spray drying system 400 comprises a spray drying vessel 410having an inlet 412 at its upper end portion in which is mounted anatomizer nozzle 418 as shown. The atomizer nozzle 418 receives spraydryable material via spray dryable material feed line 422, and theatomizer nozzle generates a spray of particles of the material to bespray dried, as discharged into the interior volume 420 of the spraydrying vessel for contact with drying fluid therein.

The spray drying vessel 410 includes a main chamber portion 414, and alower portion 416. The lower portion 416 is adapted for fluidized bedoperation, being supplied by drying fluid inlet 442 from drying fluidfeed line 444 with drying fluid that is introduced so as to effectfluidization of particles in the lower portion of the spray dryingvessel. This in situ fluidized bed in the lower portion of the spraydrying vessel is necessary to achieve a spray dried powder product, dueto the previously noted short residence time of sprayed particles in thefluidized bed. The spray drying vessel 410 includes drying fluiddischarge ports 428 and 430 at the upper and outer portion of the spraydrying vessel, at which drying fluid is discharged from the spray dryingvessel and is exhausted in the drying fluid exhaust line 432.

A main flow of drying fluid 426 is introduced to the spray drying vessel410 at the drying fluid inlet 424 and the introduced drying fluidsubsequently flows downwardly in the spray drying vessel for contactwith the sprayed particles of spray dryable material in the interiorvolume 420 of the vessel.

The spray drying vessel 410 has a dried material discharge conduit 454at its lower portion, above the upper end of the fluidized bed, throughwhich dried material is discharged to a dried material product line 456for transport to downstream packaging facilities and/or otherpost-spray-drying processing operations.

The spray drying vessel 410 is provided at its main chamber portion withan array of fluid injector jets 434, 436, 438, 440, 446, 448, 450, and452, arranged as shown. Each of the fluid injector jets is coupled witha source of pressurized fluid, and the injector jets may comprise fluidinjection flow control valves that are modulatable between fully openand fully closed valve positions, to correspondingly modulate flow ofpressurized fluid through the fluid injector jets into the interiorvolume 420 of the spray drying vessel. In this manner, turbulent inputsof pressurized fluid are introduced into the main flow of drying fluidcirculating in the interior volume of the spray drying vessel, asintroduced in drying fluid inlet 424 and exhausted from the vessel indrying fluid discharge ports 428 and 430.

The pressurized fluid injector jets may variously be arranged forcontinuous or alternatively intermittent input of pressurized turbulentfluid into the spray drying vessel, and in the case of intermittentinput operation may be operated in a sequential and repetitive cyclicmanner, with a specific one or ones of the array of fluid injector jets“firing” (opening to emit a burst of pressurized turbulent fluid intothe vessel), while the other fluid injector jets in the array arequiescent with closed fluid injection flow control valves therein,followed by closure of the fluid injection flow control valve(s) of suchfluid injector jet(s)), concurrent with or followed by firing of otherfluid injector jets in a controlled pattern, so that the fluid in theinterior volume of the spray drying vessel, in contact with the sprayedmaterial particles, is actively stirred by the successive bursts ofpressurized turbulent fluid into the interior volume of the vessel.

Such active stirring by operation of the pressurized turbulent fluidinjector jets serves to homogenize the solvent vapor (e.g., water vapor)concentration in the spray drying vessel interior volume and lowers thepartial pressure of solvent vapor in the fluid in contact with theparticles, thereby enhancing mass transfer of solvent from the particleto the drying fluid, as well as increasing particle residence time inthe dryer by keeping the particles suspended in the spray drying vesselfor longer periods of time.

Accordingly, use of pressurized turbulent fluid injector jets inaccordance with the present disclosure is able to achieve remarkableenhancement in particle residence times and drying efficiency. Thisenhancement is most pronounced in low temperature operation in whichtemperature of the drying fluid introduced into the spray drying vesselfor contact with the sprayed particles is below 100° C., since such lowtemperature operation avoids formation of the dense surface layer thatotherwise is formed in high temperature spray drying processes (e.g., inwhich the drying fluid is introduced into the spray drying vessel attemperatures on the order of 180° C.-200° C.).

Thus, the low temperature spray drying process, with spray drying fluidinlet temperature ≤100° C., can be carried out with high rates of masstransfer of the solvent from the sprayed particles to the drying fluid,without the diffusional impedance represented by the dense surface layer(skin) associated with high temperature spray drying, and with the rateof mass transfer of solvent from the sprayed particles to the dryingfluid being remarkably enhanced by the injection of pressurizedturbulent fluid into the drying fluid in the spray drying vessel inaccordance with the present disclosure.

By way of a specific illustrative example, a low temperature spray dryerhaving a spray drying vessel circumference of 34.3 feet is constructedand arranged for operation with inlet temperature of the primary dryingfluid (air) to the spray drying vessel being below 100° C. The spraydrying vessel may be outfitted with 16 pressurized turbulent fluidinjector jets located along the circumference of the spray dryer in tworings of 8 jets each, with the jets being equally spaced along the dryercircumference, for injection of pressurized turbulent air. One ring maybe located 3 feet down from the top of the dryer and the second ring of8 nozzles may be located at 7 feet down from the top of the dryer. Thenozzles may be oriented so that the direction of flow of air ispositioned 10 degrees off of the radial direction and in the directionof the primary drying fluid air flow. The pressurized turbulent fluidinjector jets may be activated in radially opposing pairs, pulsing onfor 3 seconds, then after a delay of 1 second, the next adjacent pairmay be pulsed on for three seconds and repeated continuously, withsimilar operation being carried out by the second ring of pressurizedturbulent fluid injector jets. The pressurized turbulent fluid injectorjets may be pressurized to 100 psi.

FIG. 10 is a schematic representation of a spray drying process systemaccording to a further embodiment of the present disclosure.

As shown, the spray drying system 500 includes a feedstock precursorcomposition source 502, from which which a feedstock precursorcomposition is flowed in feed line 504 to a feedstock compositionprocessing unit 506, in which the precursor composition is processed ortreated to yield the spray dryable liquid composition. Such upstreamprocessing unit may be of any suitable type, and may for examplecomprise a concentration unit in which the product material to be spraydried is concentrated from a feedstock precursor compositionconcentration to a higher product material concentration in the spraydryable liquid composition discharged from the unit in line 508.

The spray dryable liquid composition may comprise a carrier oralternatively may be carrier-free in character.

As used herein, the term “carrier” refers to a solid material that isutilized in a spray dryable liquid composition, containing liquid andthe product to be spray dried, to carry and at least partially supportor at least partially encapsulate the product in the spray dried powderresulting from the spray drying operation. Carriers thus may beassociated with the product material in spray dried powders, e.g., as asubstrate, support, or associative matrix for the product material.Carriers used in spray drying operations may be of widely varying types,and may include, for example, the starch carriers disclosed in U.S. Pat.Nos. 8,939,388, 9,332,776, and 9,551,527. More generally, carriers suchas those listed in Table 1 below illustrate specific carrier materials.

TABLE 1 Spray Drying Carriers Polysaccharides: starches, modified foodstarches, native starches, maltodextrins, alginates, pectins,methylcellulose, ethylcellulose, hydrocolloids, inulin, carbohydrates,mono-, di- and tri-saccharides, soluble fibers, polydextrose Proteins:animal proteins, plant proteins, caseinates, gelatins, soy proteins, peaproteins, whey proteins, milk proteins Gums: guar gum, xanthan gum,acacia gum (gum arabic), gellan gum, and caragenan Esters: Polysorbates,stearic acid esters, oleic acid esters Lipids and waxes: coconut oil,medium chain triglyceride (MCT) oils, vegetable oils, sunflower oils,palm oils, caruba waxes, bee waxes

As used herein, the term “carrier-free” in reference to a spray dryableliquid composition means a spray dryable liquid composition that isdevoid of a carrier therein, and “carrier-free” in reference to a spraydrying process means a spray drying process carried out in the absenceof a carrier in the spray drying operation.

Referring again to FIG. 10, the spray dryable liquid composition isflowed from the feedstock composition processing unit 506 in liquidcomposition feed line 508 by pump 510 to feedstock feed line 512, fromwhich it flows into the spray dryer inlet 516 of the spray dryer vessel518, and thereupon is atomized by the atomizer 514 to generate anatomized spray 520 of the spray dryable liquid composition.Concurrently, conditioned drying fluid described more fully hereinafteris flowed in conditioned drying fluid feed line 570 to the inlet 516 ofthe spray dryer vessel 518, so that the introduced conditioned dryingfluid flows through the interior volume 522 of the spray dryer vessel518, for contact with the atomized spray of spray dryable liquidcomposition.

The conditioned drying fluid, or any portion thereof, may be flowedthrough the atomizer 514, in a so-called two-fluid atomization, or theconditioned drying fluid may be flowed into the interior volume 522 ofthe spray drying vessel 518 as a separate stream, in relation to theintroduction of the spray dryable liquid composition and its passagethrough the atomizer 514.

The atomizer 514 may be of any suitable type, and may for exampleinclude any of rotary atomizers, centrifugal atomizers, jet nozzleatomizers, nebulizers, ultrasonic atomizers, etc., and combinations oftwo or more of the foregoing. The atomizer may be electrohydrodynamic tocarry out electrohydrodynamic spray drying of the concentrated feedstockcomposition, or the atomizer may be non-electrohydrodynamic incharacter.

Regardless of the specific atomizer type and mode of atomizationemployed, the atomized spray 520 of feedstock composition is introducedto the interior volume 522 of the spray drying vessel 518, and theatomized droplets of the spray dryable liquid composition are contactedwith the conditioned drying fluid during their passage through theinterior volume to the spray dryer outlet 524, to dry the atomizeddroplets and produce the spray dried dry powder product.

The spray drying vessel 518 may optionally be provided with auxiliarydrying fluid peripheral feed lines 526, in which the arrowheads of therespective schematic feed lines 526 designate injector jets arranged tointroduce auxiliary drying fluid into the interior volume 522 of thespray drying vessel 518. The feed lines 526 and injector jets thereofthus may pass through corresponding wall openings in the spray dryingvessel 518 so that the injector jets are internally arrayed, or theinjector jets may be arranged so that they communicate with wallopenings in the spray drying vessel, injecting auxiliary drying fluidtherethrough into the interior volume 522. The auxiliary drying fluidmay be introduced into the interior volume of the spray drying vessel atsufficient pressure and flow rate to generate localized turbulence 530at or near the point of introduction into the interior volume of thespray drying vessel.

The auxiliary drying fluid peripheral feed lines 526 are illustrated asbeing coupled with an auxiliary drying fluid manifold 528 through whichthe auxiliary drying fluid is flowed to the respective feed lines 526.The auxiliary drying fluid may be introduced into the interior volume ofthe spray drying vessel in a continuous manner, or in an intermittentmanner. The auxiliary drying fluid may be introduced in bursts, e.g., ina time-sequenced manner, and the injector jets may be programmablyarranged under the monitoring and control of a central processor unitsuch as the CPU 590 illustrated in FIG. 10.

Such localized induction of turbulence is highly effective in enhancingthe diffusivity and mass transfer of liquid from the atomized dropletsof concentrated feedstock composition to the drying fluid present in thespray drying vessel.

The spray drying vessel 518, as a further enhancement of the drying ofthe atomized droplets of concentrated feedstock composition in theinterior volume of the vessel, may be equipped with an auxiliary dryingfluid central feed line 532 as shown. The auxiliary drying fluid centralfeed line 532 is provided with a series of longitudinally spaced-apartauxiliary drying fluid central feed line injector jets 534, in whichauxiliary drying fluid may be injected under sufficient pressure andflow rate conditions to generate auxiliary drying fluid injectedturbulence regions 536.

As discussed above with respect to the auxiliary drying fluid introducedinto the interior volume of the spray drying vessel through the feedlines 526 and associated injector jets, the auxiliary drying fluid maybe introduced into the interior volume of the spray drying vessel in acontinuous manner, or in an intermittent manner from the injector jets534, to provide auxiliary drying fluid injected turbulence regions 536at a central portion of the interior volume 522 in the spray dryingvessel. As discussed in connection with the peripheral feed lines andassociated injector jets, the auxiliary drying fluid may be introducedthrough the central feed line injector jets 534 in bursts, e.g., in atime-sequenced manner, and the injector jets may be programmablyarranged under the monitoring and control of a central processor unitsuch as the CPU 590 illustrated in FIG. 10.

A combination of peripheral jets and central jets such as shown in FIG.10 may be used to provide localized turbulence in the central region aswell as the outer wall region of the interior volume in the spray dryervessel, and effects a remarkably efficient spray drying process, inwhich anomalous flow behavior, such as dead zones or stagnant regions inthe interior volume, is minimized. A highly favorable hydrodynamic masstransfer environment is correspondingly provided, and the spray dryervessel as a result of such localized turbulence generation capabilitycan be substantially reduced in size and associated footprint, therebyenabling smaller pumps, compressors, blowers and other associatedancillary equipment to be employed, with consequent enhancement of thecapital equipment and operating cost characteristics of theconcentration and spray drying system.

The spray dried powder and effluent drying gas that are produced by thecontacting of the atomized droplets of concentrated feedstockcomposition with drying fluid in the interior volume of the spray dryervessel, are discharged from the spray dryer vessel in spray dryer outlet524 and flow in spray dryer effluent line 538 to cyclone 540. In lieu ofcyclone equipment, any other suitable solids/gas separation unit ofappropriate character may be employed. The cyclone 540 separates driedsolids from the drying fluid, with the dried solids flowing in driedsolids discharge line 542 to a dried solids collection vessel 544. Thedrying fluid depleted in solids content flows from the cyclone in dryingfluid discharge line 546, flowing through fines filter 548 to condenser550. In the condenser 550, the drying fluid is cooled, resulting incondensation of condensable gas therein, with condensate beingdischarged from the condenser in condensate discharge line 552.

The resulting condensate-depleted drying fluid then flows in dryingfluid recycle line 554 containing pump 556 therein to the drying fluidconditioning assembly 568, together with any needed make-up drying fluidintroduced in drying fluid make-up feed line 610. The drying fluidconditioning assembly conditions the recycle drying fluid and any addedmake-up drying fluid for flow to the spray dryer vessel 518 inconditioned drying fluid feed line 570. The drying fluid conditioningassembly may comprise a dehumidifier and/or heat exchange(heater/cooler) equipment to provide drying fluid for recycle atappropriate desired conditions of temperature and relative humidity.

Thus, drying fluid, including any necessary make-up drying fluid, may beprovided to the drying fluid conditioning assembly 568, or otherwiseprovided to the spray drying system at other appropriate location(s) inthe system, from an appropriate source, and with any appropriatepreconditioning operations being carried out by associated equipment ordevices, as needed to conduct the spray drying operation at the desiredtemperature, pressure, flow rate, composition, and relative humidity.Thus, for example, make-up drying fluid may be provided to theconditioning assembly 568 from a tank, storage vessel, or other source(e.g., the ambient atmosphere, in the case of air as such drying fluid).

As a source of auxiliary drying fluid in the system, a portion of therecycled drying fluid from drying fluid recycle line 554 may be divertedin auxiliary drying fluid feed line 572 containing flow control valve574, to the auxiliary drying fluid conditioning assembly 576. Theauxiliary drying fluid conditioning assembly 576 may be constructed andarranged in any suitable manner, and may be of a same or similarcharacter to the construction and arrangement of the drying fluidconditioning assembly 568. The auxiliary drying fluid conditioningassembly 576 thus conditions the auxiliary drying fluid so that it is atappropriate condition for the use of the auxiliary drying fluid in thesystem.

The conditioned auxiliary drying fluid flows from auxiliary drying fluidconditioning assembly 576 through auxiliary drying fluid feed line 578,from which it flows in auxiliary drying fluid feed line 580 containingpump 582 to the manifold 528, while the remainder of the conditionedauxiliary drying fluid flows in auxiliary drying fluid feed line 578 topump 584, from which it is flowed in auxiliary drying fluid feed line586 to the auxiliary drying fluid central feed line 532, forintroduction in the central region of the interior volume of the spraydryer vessel, as previously described.

It will be recognized that the system shown in FIG. 10 could bealternatively constructed and arranged with the drying fluidconditioning assembly 568 processing both the main flow of drying fluidand the auxiliary drying fluid, without the provision of a separateauxiliary drying fluid conditioning assembly 576, e.g., when the maindrying fluid and auxiliary drying fluid are of a substantially samecharacter with respect to their relevant fluid characteristics. It willalso be recognized that separate flow circulation loops for each of themain drying fluid and auxiliary drying fluid may be provided, when themain drying fluid and auxiliary drying fluid are or comprise differentgases, or are otherwise different in their relevant fluidcharacteristics.

The FIG. 10 system is shown as including a central processor unit (CPU)590 arranged to conduct monitoring and/or control operations in thesystem, and when employed in a controlling aspect, may be employed togenerate control signals for modulation of equipment and/or fluidsconditions, to maintain operation at set point or otherwise desiredoperational conditions. As mentioned, the CPU could be operationallyconnected to the conditioning assemblies 568 and 576, to controlcomponents thereof such as dehumidifiers, thermal controllers, heatexchange equipment, etc.

The CPU 590 is illustratively shown in FIG. 10 as being operativelycoupled by monitoring and/or control signal transmission lines 592, 594,596, 598, 600, 602, and 604 with pump 510, drying fluid conditioningassembly 568, auxiliary drying fluid conditioning assembly 576, flowcontrol valve 574, pump 582, pump 556, and pump 584, respectively.

It will be recognized that the specific arrangement of the CPU shown inFIG. 10 is of an illustrative character, and that the CPU may beotherwise arranged with respect to any components, elements, features,and units of the overall system, including the concentration unit 506,to monitor any suitable operational components, elements, features,units, conditions, and parameters, and/or to control any suitableoperational components, elements, features, units, conditions,parameters, and variables. For such purpose, as regards monitoringcapability, the system may comprise appropriate sensors, detectors,components, elements, features, and units. The signal transmission linesmay be bidirectional signal transmission lines, or may constitutecabling including monitoring signal transmission lines and separatecontrol signal transmission lines.

It will be appreciated that the spray drying system may be embodied inarrangements in which the contacting gas, auxiliary contacting gas,drying fluid, and auxiliary drying fluid, or any two or more thereof,may have a substantially same composition, temperature, and/or relativehumidity, thereby achieving capital equipment and operating costefficiencies with corresponding simplification of the systemrequirements. Thus, for example, all of the contacting gas, auxiliarycontacting gas, drying fluid, and auxiliary drying fluid may be air,nitrogen, argon, or other gas from a common gas source, and such commongas may be provided at a substantially same temperature and relativehumidity, so that common thermal conditioning and dehumidificationequipment can be employed.

It will thus be apparent that many varied arrangements and modes ofoperation of the pressurized turbulent fluid injector jets may beimplemented in the broad practice of the present disclosure, to achieveultrahigh efficiency spray drying operation in a wide variety of spraydrying vessels and systems.

The present disclosure in another aspect relates to a spray dryingsystem, comprising:

(a) a spray drying vessel comprising:

-   -   (i) an interior volume arranged to receive an atomized        spray-dryable material and drying fluid for contacting of the        atomized spray-dryable material with the drying fluid in the        interior volume;    -   (ii) at least one drying fluid inlet by which the drying fluid        is introduced into the interior volume for such contacting; and    -   (iii) a spray-dried material outlet communicating with the        interior volume, arranged to discharge spray-dried material and        effluent drying fluid from the vessel;

(b) an atomizer adapted to receive a spray-dryable material anddischarge the atomized spray-dryable material into the interior volumeof the vessel for such contacting;

(c) at least one turbulator adapted to generate turbulence in the dryingfluid in the interior volume of the vessel;

(d) a process control unit adapted to regulate flow rate of drying fluidinto the interior volume and flow rate of the spray-dryable material tothe atomizer so that interaction of the drying fluid with the at leastone turbulator produces turbulence in the drying fluid having aKolmogorov length less than average particle size of spray-dryablematerial droplets in the atomized spray-dryable material in the interiorvolume of the vessel.

As used herein in reference to the spray drying system of the presentdisclosure, the term “turbulator” refers to a device that is configuredto induce turbulence in drying fluid being contacted with the atomizedspray-dryable material. The device may be of any suitable type, and mayinclude any one or more jets, nozzles, injectors, and the like that areutilized for injection of secondary drying fluid into a body of primarydrying fluid so as to induce turbulence in the drying fluid forenhancement of the spray-drying operation. The device may alternativelybe of a structural type that in interaction with the drying fluidinduces turbulence in the drying fluid, e.g., twisted tapes, staticmixer devices, airfoils, Brock turbulators, wire turbulators, coilturbulators, and wall protrusion turbulators. Various kinds of suchdevices may be combined with one another in various embodiments, as maybe desirable to achieve suitable intensity of turbulence for enhancementof the rate and/or extent of drying of the atomized spray-dryablematerial.

The above-discussed spray drying system reflects the discovery thatsubstantial and unexpected increase in the rate and extent of spraydrying can be achieved by inducing turbulence in the drying fluid, inwhich the turbulence in the drying fluid is characterized by aKolmogorov length that is less than average particle size of spraydryable material droplets in the atomized spray-dryable material. TheKolmogorov length η is defined by the equation

${\eta = \sqrt[{1\text{/}4}]{\frac{v^{3}}{ɛ}}},$

where ν is the kinematic viscosity of the drying fluid, and ε is therate of dissipation of kinetic energy in the induced turbulence in thedrying fluid, as discussed more fully below.

Measurement of Kolmogorov Length Scale

In accordance with various aspects of the present disclosure, theKolmogorov length is utilized to characterize the turbulence that isinduced in the spray drying operation by the turbulator componentsassociated with the spray drying vessel.

The Kolmogorov length characterizes the energy dissipating eddies in theturbulence induced by the turbulator(s) in the fluid flow in theinterior volume of the spray drying vessel. The turbulent kinetic energyin such flow can be described in terms of a kinetic energy cascade thatdevelops spatiotemporally in the fluid in the interior volume of thespray drying vessel after turbulence is initiated. The energy introducedby the turbulator(s) into the fluid in the spray drying vessel, by fluidinjection or by flow disruption, generate hydrodynamic instabilities atlarge scales, typically characterized as the integral scale. The energyat the integral scale then is transferred to progressively smallerscales, initially through inviscid mechanisms such as vortex stretching,and subsequently through viscous dissipation into heat. When graphicallyshown on a logarithmic plot of energy as a function of wave number, thediscrete regimes of an initial energy-containing range reflecting theinduced turbulence, followed by an inertial range, followed by a finaldissipation range are readily visualized as depicting an energy cascade,with large eddies at the low wave number region transforming to eversmaller eddies and ultimately dissipating into heat. The scale at whichthe dissipative decay begins is the Kolmogorov scale

$\eta = \sqrt[{1\text{/}4}]{\frac{v^{3}}{ɛ}}$

wherein ε is the turbulence dissipation rate shown in the logarithmicplot and ν is the kinematic viscosity of the drying fluid.

The turbulent dissipation rate and Kolmogorov length are readilydetermined using standard hot wire anemometry or laser Doppleranemometry techniques. For example, hot wire anemometry may be employedto generate values of turbulence power density at a range offrequencies, with a log-log plot of turbulence power density as afunction of frequency, in Hertz, depicting the induced turbulence,inertial range, and dissipation range of the cascade, and with thedissipation range values enabling the turbulence dissipation rate to bedetermined, from which Kolmogorov length can be calculated from theabove Kolmogorov scale formula.

Advantageously, turbulence is induced in at least 5 volume % of thevolume of drying fluid in the interior volume of the vessel to providesubstantial enhancement of the spray-drying operation. More generally,the turbulence may be induced in at least 5, 10, 15, 20, 25, 30, 35, 40,45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or more volume % of thevolume of drying fluid in the interior volume of the vessel. In variousembodiments, the turbulence may be induced in at least a major portion(i.e., more than 50 volume percent) of the volume of the drying fluid inthe interior volume of the spray drying vessel. It is advantageous tomaximize the amount of the drying fluid in which turbulence is induced,and the volumetric proportion of the drying fluid in the interior volumeof the vessel in which turbulence is induced may beneficially includethe drying fluid that is in contact with the atomizer, so thatturbulence is induced as soon as possible as the drying fluid isintroduced and contacted with the atomized spray-dryable material, andturbulence thereafter is induced in the drying fluid as it passesthrough the interior volume from the inlet to the outlet of the spraydrying vessel.

By inducing turbulence in the drying fluid in accordance with thepresent disclosure, dramatic improvements in throughput and efficiencyof spray dryers can be achieved. The induction of turbulence has majorbenefit in reducing or eliminating deposition of spray-dryable materialon the interior wall surfaces of the spray dryer vessel.

The enhancement achieved by inducing turbulence in accordance with thepresent disclosure enables increased dryer throughput for a fixedinterior volume in the spray dryer, or alternatively, the design ofhigher efficiency, smaller volume spray dryers with higher throughput,thereby achieving capital equipment savings as well as reduction inoperating costs in many instances.

In instances in which average particle size of spray-dryable materialdroplets in the atomized spray-dryable material in the interior volumeof the spray-drying vessel is in a range of 50 to 300 μm, it isdesirable to induce turbulence in the drying fluid in the spray dryingoperation so that the turbulent dissipation rate exceeds 25 m²/sec³. Thespray drying operation in accordance with the present disclosure may beconducted to produce spray dried powders of average particle size in theaforementioned range of 50 to 300 μm, or in other suitable ranges suchas 75 to 250 μm, 80 to 200 μm, 85 to 150 μm, 90 to 120 μm, or otherlower or higher ranges. In general, the spray drying operation isadvantageously conducted so that the turbulent dissipation rate isgreater than at least one of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55,60, 65, 70, 75, 80, 85, 90, 95, 100, 150, 200, 250, 300, 400, 500, 600,700, 800, 900, or 1000, m²/sec³, e.g., in specific ranges in which thelower end point value is one of the aforementioned numeric values andthe upper end point value is one of the aforementioned numeric valuesexceeding the lower end point value.

Thus, the spray drying system may include at least one turbulator thatcomprises one or more nozzles configured to inject pressurized secondarydrying fluid into the interior volume of the vessel, e.g., an array ofnozzles in a geometrically regular or irregular arrangement.

Additionally, or alternatively, the at least one turbulator employed inthe spray drying system may comprise any one or more of twisted tapes,static mixer devices, airfoils, Brock turbulators, wire turbulators,coil turbulators, and wall protrusion turbulators.

In the spray drying system, the atomizer may be of any suitable type andmay for example comprise nozzle atomizers, applied charge atomizers,nebulizers, rotary atomizers, ultrasonic atomizers, or atomizers of anyother suitable type.

The spray drying system as above described may operationally comprise adrying fluid source coupled to the at least one drying fluid inlet indrying fluid supply relationship with the spray drying vessel. Suchdrying source may be constituted to supply the drying fluid to the atleast one drying fluid inlet of the spray drying vessel, with the dryingfluid comprising air, oxygen-enriched air, oxygen, nitrogen, argon,krypton, neon, helium, or a gas mixture comprising two or more of theforegoing drying fluid species. In various embodiments, the drying fluidsource may be constituted to supply the drying fluid to the at least onedrying fluid inlet of the spray drying vessel at temperature below atleast one of 120° C., 115° C., 110° C., 100° C., 95° C., 90° C., 85° C.,80° C., 75° C., 70° C., 65° C., 60° C., 55° C., 50° C., 45° C., 40° C.,35° C., 30° C., 25° C., and 20° C., and above freezing temperature ofliquid to be volatilized for spray drying of the spray-dryable material.

In various embodiments, the drying fluid source may be constituted tosupply the drying fluid to the at least one drying fluid inlet of thespray drying vessel at temperature below 100° C., and above freezingtemperature of liquid to be volatilized for spray drying of thespray-dryable material.

The spray drying system variously described above may operationallycomprise a spray-dryable material source arranged in spray-dryablematerial supply relationship to the atomizer.

The spray drying system in various implementations may utilize aspray-dryable material source comprising the spray-dryable material in acarrier-free composition. Alternatively, the spray dryable materialsource may comprise the spray-dryable material in a carrier-comprisingcomposition.

The spray drying system as variously described above may be constructedand arranged so that the process control unit is adapted to regulateflow rate of drying fluid into the interior volume and flow rate of thespray-dryable material to the atomizer so that the average particle sizeof the spray-dryable material droplets in the atomized spray-dryablematerial in the interior volume of the vessel is in a range of from 50to 300 μm.

In specific embodiments, the process control unit may be adapted toregulate flow rate of drying fluid into the interior volume and flowrate of the spray-dryable material to the atomizer so that turbulencedissipation rate of said turbulence exceeds 25 m²/sec³.

In general, the process control unit may be constructed and arranged toinduce turbulence in the drying fluid in any suitable manner. Forexample, the process control unit may be configured to produceintermittent turbulence in the drying fluid, or the process control unitmay be configured to produce continuous turbulence in the drying fluid.

The variously above-described spray drying system may be configured forapplied charge spray drying (commonly referred to as electrostatic spraydrying).

The disclosure in a further aspect relates to a process for producing aspray-dried material, comprising:

generating an atomized spray-dryable material;

contacting the atomized spray-dryable material with drying fluid to formspray-dried material;

recovering the spray-dried material from the drying fluid; and

during such contacting, inducing turbulence in the drying fluid having aKolmogorov length less than average particle size of spray-dryablematerial droplets in the atomized spray-dryable material.

The process may be conducted, in which the turbulence is induced in atleast 5 volume % of the volume of drying fluid engaged in thecontacting, e.g., in at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55,60, 65, 70, 75, 80, 85, 90, 95, or more volume % of the volume of dryingfluid engaged in the contacting.

The turbulence in such process may be induced by injection ofpressurized secondary drying fluid. Additionally, or alternatively, theturbulence may be induced by interaction of the drying fluid with aturbulator comprising at least one selected from among twisted tapes,static mixer devices, airfoils, Brock turbulators, wire turbulators,coil turbulators, and wall protrusion turbulators.

In the process, the atomized spray-dryable material may be generated byan atomizer comprising at least one selected from among nozzleatomizers, applied charge atomizers, nebulizers, rotary atomizers, andultrasonic atomizers. Alternatively, any other suitable type or types ofatomizer may be employed.

The spray-drying process may be conducted, in which the drying fluidcomprises air, oxygen-enriched air, oxygen, nitrogen, argon, krypton,neon, helium, or a gas mixture comprising two or more of the foregoingdrying fluid species.

The process may be conducted, in which the drying fluid is introduced tothe contacting at temperature below at least one of 120° C., 115° C.,110° C., 100° C., 95° C., 90° C., 85° C., 80° C., 75° C., 70° C., 65°C., 60° C., 55° C., 50° C., 45° C., 40° C., 35° C., 30° C., 25° C., and20° C., and above freezing temperature of liquid to be volatilized toform the spray-dryable material.

The process may be conducted, in which the average particle size of thespray-dryable material droplets in the atomized spray-dryable materialin the contacting is in a range of from 50 to 300 μm.

the process may be conducted, in which turbulence dissipation rate ofthe turbulence induced during said contacting exceeds 25 m²/sec³.

In various embodiments, the process may be carried out, in which thedrying fluid is introduced to the contacting at temperature below 100°C. and above freezing temperature of liquid to be volatilized to formthe spray-dried material.

The process may be carried out in which the atomized spray-dryablematerial is carrier-free, or alternatively, wherein the atomizedspray-dryable material comprises a carrier.

The process is susceptible to operation in which turbulence is inducedintermittently during the contacting, or alternatively, the turbulencemay be induced continuously during the contacting.

As alluded to above, in the discussion of the spray drying system, theprocess may be carried out in which the spray-dryable material dropletsin the atomized spray-dryable material are electrically charged.

The disclosure in a further aspect relates to a spray drying system,comprising:

(a) a spray drying vessel comprising:

-   -   (i) an interior volume arranged to receive an atomized        spray-dryable material and drying fluid for contacting of the        atomized spray-dryable material with the drying fluid in the        interior volume;    -   (ii) at least one drying fluid inlet by which the drying fluid        is introduced into the interior volume for said contacting; and    -   (iii) a spray-dried material outlet communicating with the        interior volume, arranged to discharge spray-dried material and        effluent drying fluid from the vessel;

(b) an atomizer adapted to receive a spray-dryable material anddischarge the atomized spray-dryable material into the interior volumeof the vessel for said contacting;

(c) at least one turbulator adapted to generate turbulence in the dryingfluid in the interior volume of the vessel;

(d) a process control unit adapted to regulate flow rate of drying fluidinto the interior volume and flow rate of the spray-dryable material tothe atomizer so that interaction of the drying fluid with the at leastone turbulator produces turbulence in the drying fluid producing aturbulence dissipation rate exceeding 25 m²/see.

Such spray drying system may be utilized with any of the components,features, and accessories described hereinabove. For example, such spraydrying system may be adapted for low temperature operation, such as attemperature below 100° C. of the drying fluid introduced to the interiorvolume of the spray drying vessel, as previously described herein.

The disclosure relates in a further aspect to a process for producing aspray-dried material, comprising:

generating an atomized spray-dryable material;

contacting the atomized spray-dryable material with drying fluid to formspray-dried material;

recovering the spray-dried material from the drying fluid; and

during said contacting, inducing turbulence in the drying fluidproducing a turbulence dissipation rate exceeding 25 m²/see.

Such spray drying process may likewise be implemented with any of theconditions, limitations, and specifications described hereinabove. Forexample, such spray drying process may be adapted for low temperatureoperation, such as that temperature below 100° C. of the drying fluidcontacted with the atomized spray-dryable material, as previouslydescribed herein.

The features, aspects, and advantages of the spray drying system andprocess of the present disclosure are further understood with respect tothe following illustrative Example.

Example 1

A comparison was made of two low temperature operation spray dryers.Both dryers are constructed and arranged to operate with an inlet airtemperature of the drying fluid of 42° C., and drying fluid relativehumidity <1%. Dryer 1 has an internal volume of 12,175 gallons (53.6m³), while Dryer 2 has an internal volume of 3,870 gallons (17.05 m³).Both dryers employ identical atomizers operating under identicalconditions. The volumetric airflow in Dryer 1 is 2200 cfm, while that inDryer 2 is 1800 cfm. Dryer 1 has a simple swirl type inlet. Dryer 2 hasa dual track swirl inlet designed to produce high levels of turbulencein the immediate vicinity of the atomizer.

Dryer 2 exhibits an increased inlet air velocity and turbulencedissipation rates well above 1000 (m²/s³), with Kolmogorov lengths wellbelow 100 micrometers.

Graphs of the calculated radial distribution of the turbulencedissipation rate as a function of radius for both Dryer 1 and Dryer 2are shown in FIGS. 11 and 12.

FIG. 11 is a graph of turbulent dissipation rate, in m²/sec³, as afunction of radial distance in an interior volume of a spray dryingvessel, at different vertical heights in such interior volume, for afirst illustrative spray drying system (Dryer 1).

FIG. 12 is a graph of turbulent dissipation rate, in m²/sec³, as afunction of radial distance in an interior volume of a spray dryingvessel, at different vertical heights in such interior volume, for asecond illustrative spray drying system (Dryer 2).

The turbulence dissipation rate in Dryer 2 is over two orders ofmagnitude larger than that in Dryer 1 at the peak region. The radialextent of the turbulent dissipation rate at values greater than 25 m²/s³in the upper region of the dryer 1 is ˜0.25 m from the dryer centerline,while it extends outward to >1 m for Dryer 2. At the highest levels ofturbulent dissipation rate in Dryer 2, the Kolmogorov length is on theorder of 9 micrometers, with the ratio

$\frac{\eta}{{do}_{o}} < 0.09$

for 100 micrometer diameter particles.

The same fruit punch slurry was dried in both dryers. Dryer 1's highestrun rate was 1.6 lb/min. Dryer 2's highest run rate was 2.4 lb/min, or40% faster in 31.8% of the volume of Dryer 1 using 400 cfm less airflow. These results evidence the magnitude of enhancement that isachievable utilizing effective inducement of turbulence in the dryingfluid.

FIG. 13 is a schematic representation of a spray drying system 700according to a further embodiment of the present disclosure.

The spray drying system 700 shown in FIG. 13 includes a spray dryingvessel 702 with interior volume 704. In the interior volume is disposedan atomizer 706 depending downwardly from inlet feed assembly 708. Theinlet feed assembly 708 includes spray dryable composition feed line 710and drying fluid feed line 712, arranged so that the spray dryablecomposition is flowed from a suitable source (not shown in FIG. 13)through feed line 710 to the atomizer 706. The atomizer operates togenerate an atomized spray-dryable composition discharged into theinterior volume 704 of the spray dryer vessel 702. The drying fluid feedline 712 flows drying fluid from a source (not shown) through the inletfeed assembly 708 to the interior volume 704 of the spray dryer vessel702.

The spray dryer vessel 702 is equipped with a plurality of jet nozzleinjectors 714, 716, 718, 720, 722, and 724, each having a feedlinejoined to a source of secondary drying fluid. The jet nozzle injectorsinjected the secondary drying fluid at suitable flow rate and pressureconditions to induce turbulence in the primary drying fluid in theinterior volume 704.

In addition to the jet nozzle injectors, the spray dryer vessel 702 alsoincludes a series of wall-mounted turbulators 728, 730, 732, and 734,which are sized and shaped to cause turbulence in the drying fluidcontacting them during flow of the drying fluid through the interiorvolume of the vessel. At the lower end of the conical lower portion ofthe vessel is an effluent discharge line 726, by which spray-driedmaterial and effluent drying fluid or discharged from the vessel. Thespray dried material and effluent drying fluid may be passed to acyclone separator in which the spray dried material is recovered fromthe effluent drying fluid, with the effluent drying fluid then beingprocessed for recycle in the system, in whole or part, if desired, oralternatively being vented from the system, with fresh drying fluidbeing introduced as above described.

The spray drying system shown in FIG. 13 further comprises a processcontrol unit 736 that is shown schematically with process control signaltransmission lines 738 and 740, thereby schematically signifying thatthe process control unit is operatively linked with the delivery linesso as to regulate the flow rate of drying fluid into the interior volumeand flow rate of the spray-dryable material to the atomizer so thatinteraction of the drying fluid with the at least one turbulatorproduces turbulence in the drying fluid having a Kolmogorov length lessthan average particle size of spray-dryable material droplets in theatomized spray-dryable material in the interior volume of the vessel.Such arrangement may thus include respective flow control valves in thespray dryable composition feed line 710 and drying fluid feedline 712for such purpose.

Additionally, or alternatively, the process control unit may be adaptedto regulate flow rate of drying fluid into the interior volume and flowrate of the spray-dryable material to the atomizer so that the averageparticle size of the spray-dryable material droplets in the atomizedspray-dryable material in the interior volume of the vessel is in arange of from 50 to 300 μm.

Additionally, or alternatively, the process control unit may be adaptedto regulate flow rate of drying fluid into the interior volume and flowrate of the spray-dryable material to the atomizer so that turbulencedissipation rate of such turbulence exceeds 25 m²/sec³.

Additionally, or alternatively, the process control unit may be adaptedto controllably operate a dehumidification assembly so that the dryingfluid is controlled at a predetermined relative humidity, in a relativehumidity range or below a predetermined maximum value, as describedhereinabove in relation to the dehumidification assembly.

Additionally, or alternatively, the process control unit may be adaptedto controllably regulate temperature of the drying fluid (primary and/orsecondary drying fluid) so that the temperature is within apredetermined range or is below a predetermined maximum temperaturevalue. In various embodiments, the process control unit may be adaptedto regulate temperature of the drying fluid so that the spray dryingsystem operates in a low temperature (<100° C. inlet temperature) modeof operation.

The process control unit may be configured in any suitable manner, andmay be constructed and arranged to conduct additional monitoring,sensing, and process control operations. The process control unit may beof any suitable type, and may for example comprise microprocessor(s),microcontroller(s), general or special purpose programmable computer(s),programmable logic controller(s), or the like, which areprogrammatically arranged for carrying out spray drying processoperations by means of hardware, software, or firmware that is providedfor such purpose in the process control unit. The process control unitmay comprise memory that is of random-access, read-only, flash, or othercharacter, and may comprise a database of operational protocols or otherinformation for operational performance of the system.

It will be recognized that the use of induced turbulence in accordancewith the present disclosure enables the achievement of highly effectivespray drying operations for production of spray dried materials ofwidely varying characters. The use of induced turbulence may be employedto enable low temperature spray drying operation, e.g., spray dryingoperation at drying fluid inlet temperature below 100° C. or lower.

While the disclosure has been set forth herein in reference to specificaspects, features and illustrative embodiments, it will be appreciatedthat the utility of the disclosure is not thus limited, but ratherextends to and encompasses numerous other variations, modifications andalternative embodiments, as will suggest themselves to those of ordinaryskill in the field of the present disclosure, based on the descriptionherein. Correspondingly, the invention as hereinafter claimed isintended to be broadly construed and interpreted, as including all suchvariations, modifications and alternative embodiments, within its spiritand scope.

What is claimed is:
 1. A spray drying system, comprising: (a) a spraydrying vessel comprising: (i) an interior volume arranged to receive anatomized spray-dryable material and drying fluid for contacting of theatomized spray-dryable material with the drying fluid in the interiorvolume; (ii) at least one drying fluid inlet by which the drying fluidis introduced into the interior volume for said contacting; and (iii) aspray-dried material outlet communicating with the interior volume,arranged to discharge spray-dried material and effluent drying fluidfrom the vessel; (b) an atomizer adapted to receive a spray-dryablematerial and discharge the atomized spray-dryable material into theinterior volume of the vessel for said contacting; (c) turbulatorspositioned to generate localized turbulence in the drying fluidthroughout the interior volume of the vessel; and (d) a process controlunit adapted to regulate flow rate of drying fluid into the interiorvolume and flow rate of the spray-dryable material to the atomizer sothat interaction of the drying fluid with the turbulators produceslocalized turbulence in the drying fluid throughout the interior volumeof the vessel.
 2. The spray drying system of claim 1, wherein theturbulators and process control unit are adapted to cooperativelyprovide a turbulence dissipation rate of said localized turbulence inthe drying fluid in the interior volume of the vessel that exceeds 25m²/sec³.
 3. The spray drying system of claim 1, wherein the turbulatorsand process control unit are adapted to cooperatively provide saidlocalized turbulence in the drying fluid in the interior volume of thevessel, wherein said localized turbulence is characterized by aKolmogorov length that is less than an average particle size of spraydryable material droplets in the atomized spray-dryable material.
 4. Thespray drying system of claim 1, wherein said process control unit isadapted to regulate temperature of the drying fluid so that the spraydrying system operates in a low temperature mode of operation.
 5. Thespray drying system of claim 1, wherein the turbulators comprise nozzlesconfigured to inject pressurized secondary drying fluid into theinterior volume of the vessel.
 6. The spray drying system of claim 5,wherein at least some of the nozzles are provided along a wall of thevessel.
 7. The spray drying system of claim 5, wherein at least some ofthe nozzles are provided at a central region of the interior volume ofthe vessel.
 8. The spray drying system of claim 5, wherein said nozzlescomprise nozzles provided along a wall of the vessel and nozzlesprovided at a central region of the interior volume of the vessel. 9.The spray drying system of claim 1, wherein the atomizer comprises atleast one selected from among nozzle atomizers, applied chargeatomizers, nebulizers, rotary atomizers, and ultrasonic atomizers. 10.The spray drying system of claim 1, comprising a drying fluid sourcecoupled to the at least one drying fluid inlet in drying fluid supplyrelationship with the spray drying vessel.
 11. The spray drying systemof claim 10, wherein the drying fluid source is constituted to supplythe drying fluid to the at least one drying fluid inlet of the spraydrying vessel, the drying fluid comprising air, oxygen-enriched air,oxygen, nitrogen, argon, krypton, neon, helium, or a gas mixturecomprising two or more of the foregoing drying fluid species.
 12. Thespray drying system of claim 10, wherein the drying fluid source isconstituted to supply the drying fluid to the at least one drying fluidinlet of the spray drying vessel at temperature below at least one of120° C., 115° C., 110° C., 100° C., 95° C., 90° C., 85° C., 80° C., 75°C., 70° C., 65° C., 60° C., 55° C., 50° C., 45° C., 40° C., 35° C., 30°C., 25° C., and 20° C., and above freezing temperature of liquid to bevolatilized for spray drying of the spray-dryable material.
 13. Thespray drying system of claim 10, wherein the drying fluid source isconstituted to supply the drying fluid to the at least one drying fluidinlet of the spray drying vessel at temperature below 100° C., and abovefreezing temperature of liquid to be volatilized for spray drying of thespray-dryable material.
 14. The spray drying system of claim 1,comprising a spray-dryable material source arranged in spray-dryablematerial supply relationship to the atomizer.
 15. The spray dryingsystem of claim 14, wherein the spray-dryable material source containsspray-dryable material having a viscosity in a range of 500 to 16,000mPa-s and a solvent content that does not exceed 50% by weight, based ontotal weight of the spray-dryable material.
 16. The spray dryable systemof claim 1, comprising a dehumidification assembly arranged todehumidify the drying fluid so that it is introduced by the at least onedrying fluid inlet into the interior volume of the vessel for saidcontacting, at a relative humidity below 35%.
 17. The spray dryingsystem of claim 1, as configured for electrostatic spray-drying.
 18. Thespray drying system of claim 1, comprising a single step spray dryingsystem.
 19. A process for producing a spray-dried material, comprising:generating an atomized spray-dryable material; contacting the atomizedspray-dryable material with drying fluid to form spray-dried material;recovering the spray-dried material from the drying fluid; and duringsaid contacting, inducing localized turbulence throughout said dryingfluid engaged in said contacting.
 20. The process of claim 19, whereinsaid localized turbulence has a turbulence dissipation rate that exceeds25 m²/sec³.
 21. The process of claim 19, wherein said localizedturbulence is characterized by a Kolmogorov length that is less than anaverage particle size of spray dryable material droplets in the atomizedspray-dryable material.
 22. The process of claim 19, wherein saidlocalized turbulence is induced at least in part by injectingpressurized secondary drying fluid into said drying fluid engaged insaid contacting.
 23. The process of claim 19, wherein the drying fluidcomprises air, oxygen-enriched air, oxygen, nitrogen, argon, krypton,neon, helium, or a gas mixture comprising two or more of the foregoingdrying fluid species.
 24. The process of claim 19, wherein said dryingfluid is introduced to the contacting at temperature below at least oneof 120° C., 115° C., 110° C., 100° C., 95° C., 90° C., 85° C., 80° C.,75° C., 70° C., 65° C., 60° C., 55° C., 50° C., 45° C., 40° C., 35° C.,30° C., 25° C., and 20° C., and above freezing temperature of liquid tobe volatilized to form said spray-dried material.
 25. The process ofclaim 19, wherein said drying fluid is introduced to the contacting attemperature below 100° C., and above freezing temperature of liquid tobe volatilized to form said spray-dried material.
 26. The process ofclaim 19, wherein average particle size of spray-dryable materialdroplets in the atomized spray-dryable material in said contacting is ina range of from 50 to 300 μm.
 27. The process of claim 19, wherein saiddrying fluid is introduced to said contacting at relative humidity below35%.
 28. The process of claim 19, wherein said spray-dryable materialhas a viscosity in a range of 500 to 16,000 mPa-s and a solvent contentthat does not exceed 50% by weight, based on total weight of thespray-dryable material.
 29. The process of claim 19, wherein anelectrostatic charge is applied to the atomized spray-dryable materialor to spray-dryable material from which the atomized spray-dryablematerial is generated.
 30. The process of claim 29, wherein theelectrostatic charge is applied at a voltage in a range of from 0.5 to75 kV.